I've now found some more information that could shed some light on his true age. First, a baptismal record from 1915 in Vienna - his name is given as Napoleon Boleslaus Reiter and his parents are said to be Leopold Reiter and Sofia Weinberger, which matches with the Geni profile. His place of birth is given as Tysmenytsia in present-day Ukraine, not Bucharest as previously thought. His birth date is also given as 7 May 1892 - not 7 March 1892, though as this record is still from 23 years after his birth I don't think it can be considered concrete proof of his birth being on that date. The record is also in German - which I'm not fluent in - so it's possible I've missed something.

A brief court transcript featured in a news article gives some more insight into his life: namely that he was a university graduate, and that he had worked in Poland, Belgium, and Romania:

Notably, a birth date of 7 May 1892 would've made him the oldest living man in the UK for over a year. 

https://classifieds.belfasttelegraph.co.uk/advert/northern-ireland/family-notices/death-notices/512530/Mccullagh-Jane-Whiteford-jean-n-e-Lyttle

The oldest living person in Northern Ireland is now believed to be Agnes Thompson of Belfast (b. 2 September 1915). 

Scotland's oldest known living person, Marion Dawson, on her 109th birthday (source: https://www.houstonkillellankirk.org/church-record)

1. Marion Dawson (b. 19 Jan 1913), 109, of Houston, Renfrewshire
2. Isabella Donald (b. 12 Dec 1913), 108, of Oldmeldrum, Aberdeenshire
3. Ethel McKay (b. 2 Nov 1914), 107, of Cupar, Fife
4. Ailsa Stewart (b. 21 Dec 1914), 107, of Campbeltown, Argyll and Bute (b. India)
5. David Crawford (b. 21 Mar 1915), 107, of Haddington, East Lothian (male)
6. Anne Stewart (b. 22 Mar 1915), 107, of Dalkeith, Midlothian (birthday not confirmed)
7. Anonymous (b. 10 Apr 1915), 107, of Glasgow (birthday not confirmed)
8. Christina Paterson (b. 28 May 1915), 106, of Cupar, Fife
9. Annie McCaskie (b. 4 Jul 1915), 106, of Biggar, South Lanarkshire
10. David Thomson (b. 17 Aug 1915), 106, of Forth, South Lanarkshire (male)
11. Elizabeth Farquharson (b. 18 Aug 1915), 106, of Edinburgh
12. Alice Goode (b. 30 Sep 1915), 106, of Inverness, Highland
13. Anonymous (b. 3 Oct 1915), 106, of Aberdeen
14. Anonymous (b. 4 Nov 1915), 106, of Denny, Falkirk
15. Mabel Graham (b. 20 Feb 1916), 106, of Largs, North Ayrshire
16. Cathy Smith (b. 22 Feb 1916), 106, of Montrose, Angus
17. Agnes McAlpine (b. 1 Mar 1916), 106, of Edinburgh

Currently 27 people known aged 105+ (true number likely 45-50) 

Trivia & factoids

Marion Dawson is currently the thirtieth-oldest person in Scotland ever, whilst Isabella Donald is sixty-fifth. 

David Crawford and David Thomson are the ninth and thirteenth-oldest men in Scotland ever respectively.

Elizabeth Farquharson and her late sister Anne Robson (1911-2020) are the oldest known pair of Scottish siblings ever, with a combined age of 215 years, 17 days.

Cathy Smith regularly attended the gym until she was 104, when she was forced to stop due to COVID. At the age of 106, she is still able to perform high-kicks!

1. Michael O'Connor (Muckross, Kerry) (b. 13 October 1913), 108 y.o. Doyen of Ireland
2. Mathew Crowley (Youghal, Cork) (b. 12 May 1914), 107 y.o.
3. Mairin Hughes (Chapellizod, Dublin) (b. 22 May 1914 in the UK), 107 y.o. Doyenne of Ireland
4. Carmel Geoghan (Dublin, Dublin) (b. 22 July 1914), 107 y.o.
5. Kitty Jeffery (Cloyne, Cork) (b. 12 November 1914), 107 y.o.
6. Mary Gaughan (Erris , Mayo) (b. 2 February 1915), 107 y.o.
7. Phyllis Furness (Oughterard, Galway) (b. 23 May 1915 in the UK), 106 y.o.
8. Bridget Tierney (Loughduff, Cavan) (b. 3 July 1915), 106 y.o. 
9. Hannah O'Shea (Killarney, Kerry) (b. 23 September 1915), 106 y.o. 
10. Bernie Campbell (Rathcoffey, Kildare) (b. 26 November 1915), 106 y.o. 

1. Ethel May Caterham (Ash Vale, Surrey, ENG) (b. 21 August 1909), 112 y.o.
2. Rose May Eaton (Surrey, ENG) (b. 23 August 1909), 112 y.o.
3. Ada Thompson (Thwaites, West Yorkshire, ENG) (b. 28 November 1910), 111 y.o.
4. Edna Strickland (Hounslow, London, ENG) (b. 6 march 1911), 111 y.o. 
5. Gladys Mathilda Cloke (Madeley, Shropshire, ENG) (b. 24 July 1911), 110 y.o. 
6. Mary Florence Walker (Croydon, London, ENG) (b. 28 August 1911), 110 y.o.
7. Mary Letitia Keir (Llandeilo, Carmarthenshire, WAL) (b. 3 March 1912), 110 y.o.
8. Margaret Hammond (Normanton, West Yorkshire, ENG) (b. 25 May 1912), 109 y.o. 
9. Olive Finlay (Whickham, Tyne and Wear, ENG) (b. 3 August 1912), 109 y.o. 
10. Mary Ann Anwyl (Cobham, Surrey, ENG) (b. 23 August 1912), 109 y.o.