I've read the article, but I'm not convinced by the explanation provided.
To my mind, there are a number of problems with it.
Firstly, it all rests on the testimony of an anonymous individual who started work at that particular fire station 10 years after the event. This means, at best, this information is second hand, but also would have undoubtedly been subject to certain 'changes' and 'revisions' that inevitably occur with any story that is re-told at different points by different individuals over the course of a 10 years plus period after the event.
I don't think it's beyond the realms of possibility that when the firemen heard about this incident they joked with themselves that it was just a colleague, 'big john', in a specialist suit and, as time passed and personnel changed, this in-joke became an accepted 'fact'.
Secondly, a lot of the explanation relies on assumptions made by the author. The author assumes Ken Edwards was drunk. The author assumes the fireman who was trotted out by police to test Edwards, was wearing a 'different' specialist suit. The author assumes the firemen and police would've 'closed ranks' when questioned by UFO investigators.
Lastly, there are a lot of things about the encounter that this article does not explain and leaves out altogether.
For example, the article neglects to mention that Ken Edwards, in fact, saw the Silver Man twice. The second occasion was a few days after the first incident when he had returned to the scene with a UFO investigator. If we are to believe, as the article assumes, that the 'hoaxing' firemen were so concerned by potential sackings/inquiries that they would not come clean and admit the hoax, then why would they take the risk of performing a second hoax so soon after the first, given all the publicity the first generated? It doesn't add up.
There are lots of other details of the encounter, not mentioned in the article, that this explanation fails to explain away: missing time; Ken Edwards' strange 'sunburn' injuries; Edwards' description of the Silver Man does not tally with that of a man in a protective suit ("arms that were not attached at its shoulders, but stuck straight out of its chest") and the 'paralysis' Edwards experience during the encounter to name but a few.
I'm not ruling out a hoax as a possible explanation. But, to my mind, despite the claims to the contrary in the article, the Risley Silver Man remains unexplained.