It seems to me, with my limited experience doing this (never) and less limited experience witnessing it, that in game the engine "blip" allows a similar loss of air speed to cutting throttle, but the e retention seems to me to be considerably better with those who shut down vs cutting throttle. I.E. if I am already closing on them while throttling back and they cut off suddenly, I have gone full power yet they can stay on my six and climb, where those that have simply throttled back do not. Not a case of dissimilar aircraft either.
Again, this is my experience with seeing it and my attempts to understand it. Gaming? Probably but there are plenty of other ways that it happens without this level of complaint.
People complain about it because they feel like it gives them an excuse for why they lost:
"Well, he used a stupid gaming mechanic - in a game - to shoot me down. If I can whine and push HTC into fixing it, he can't kill me anymore and I'll be able to beat him next time."
A great example of the mentality surrounding this issue is a recent encounter I had with TwinBoom. He dove on me in an A-20 while I was flying a D9. I do cut my engine occasionally, and I had done it to him (and killed him) several sorties before. However, on this occasion, I did not cut my engine - I simply throttled all the way back. He overshot me due to poor speed control, and then dove to the deck, accusing me of cutting my engine and crying on 200 about how I needed to "engine burp" and that he outflew me, as my supposed cutting my engine (which never happened) was a sign of conceding to his better piloting skills. He then ran into his ack. His complaint had nothing to do with realism, but rather an excuse for why he overshot and lost his position, even though no such tactic was used.
For him, as with 99.9% of everyone else who complains about it, it's not about realism - it's about excuses. If realism were the primary concern, the complaints regarding engine "cutting" would be almost non-existent and we'd be hearing complaints about WEP on takeoff, flaps that auto-retract (instead of jamming or being ripped off), etc.
The irony here, assuming that there
is some sort of measurable advantage to cutting one's engine, is that someone intelligent enough to figure out such a tactic has likely already invested more effort into learning the game and it's many other nuances much more than the pilot complaining about the tactic. Ergo, they'd likely beat you regardless of what tactics they chose to use. Of course, there's the glaring issue that no one can even substantiate claims that any kind of advantage comes from engine cutting, and even Hitech has stated there is none. In fact, all evidence points to engine cutting putting the pilot at a disadvantage. But, I digress.
It's VERY easy to kill an engine in flight and restart it - anyone who's pursued their multi-engine rating can do this without even thinking about it. Combat pilots would have memorized the same flow and been able to start/restart effortlessly. The only reason we don't see examples of it is because there was no reason or advantage to do so, which brings us to the crux of the argument.
If cutting ones engine in real life produces no benefit or effect, then why do we care here? If it's for realism, then you would both concede it IS realistic to be able to cut your engine, while at the same time agreeing it's a non-issue in comparison to the realism (or lack of) with other flight mechanics. That said, if we're going to insist that cutting one's engine does produce an advantage, then trying to "fix" engine on/off is completely backwards. If toggling your engine in flight gives a noticeable advantage, then there's an issue with the flight model that needs to be addressed - it's as simple as that.