The only argument for no S on the link you posted I see is someone from 2007 quoting "encyclopedia.thefreedictionary.com", which was a copy of the old wikipedia page and has since been deleted and changed to Vickers-Armstrongs with S. The other person quoted various documents which show it is Vickers-Armstrongs, as do all of the original equipment data plates.
https://i.etsystatic.com/13649851/r/il/ff2e94/2134003525/il_fullxfull.2134003525- _3anb.jpg
https://pbs.twimg.com/media/GENikTGWUAANqS6?format=jpg&name=large
https://i.ebayimg.com/images/g/CQYAAOSwnipWbitA/s-l1600.jpg
https://shop.unigreenscheme.co.uk/files/ITEM-37040-013.jpg?v=RIvbUlJBWt
A British historian I know, Craig Moore, as said in the past that the company merger documents in the Kew archive say Vickers-Armstrongs. He's hard to get ahold of though so I don't know if I can get a copy of that to prove it.

These two manuals are from 1936 and 1933 respectively
https://i.imgur.com/j0wx7VQ.jpeg
https://i.imgur.com/edUXCiv.jpeg