Welcome to ribnet!
I can't say for sure here without more digging to check your engine, but I doubt it unless you are fuel injected. If you just killed the spark on one cyl of a traditional 2- stroke it would still ingest fuel whether it's sparking or not, & so oil itself up. Also as you point out without a pressure relief on the cyl it gets quite lumpy! Killing cyls at idle is OJK if you have a multi cylinder fuel injected machine, but hightly unlikely on a 3 -pot. (this is where a raft of people will be along to prove me wrong!
Best thing to do is to swap plugs, coils & HT leads (assuming they're not all integral) around one at a time & see if the problem follows the plugs or the coils. My old Yam ran like a dog at idle - cured with a new set of plugs. (I later meggered the plugs - one was part shorting)