I’m 100% sure this happened to me, but of course short of walking away, and having them come back saying the other offers had magically disappeared, there was no way to prove it.
Some EAs (not all, I know) are definitely up to all sorts.
Another time, a very pleasant and plausible EA went through the ‘official’ motions of having a property on the market, showing it to viewers, etc., when in reality it was going to be sold very cheaply to someone already designated. (The property - a rental - belonged to one of the EA staff - they did say this in the blurb, since they’re obliged to.)
I do know this, because when I made an offer, very close to asking, he said yes, but only if I could exchange that same day! WTF? Of course I couldn’t - I’d never heard of such a thing, but he very smoothly told me it wasn’t unusual.
I was still nonplussed until about 3 months later, when I checked sold prices and saw that it had gone for WAY below my offer - it was about £180k compared to my offer of £220k - ish.
Evidently it had gone to a mate or a son/daughter of whoever it was, and the relatively low price meant avoidance of a lot of the CGT that would have been due, since it had been a rental and prices had shot up during the previous few years.
The best joke was, while we were standing outside, waiting to view the place, he told me during his very friendly chat, that his father was a vicar!!
Nowadays I’d take anything an EA may say with a colossal pinch of salt.