I think the short course for Aug through March (8 months) and long course April through July is your typical pool arrangement for virtually all club teams, which is where virtually all of the Oly swimmers were developed. They seem to do pretty well swimming SCY for 2/3rds of the year. Sure, you need some solid long course training for endurance but speed is best developed in the shorter pool.
this is just a anecdote and not meant to provide too much value to the thread:
About 20-25 years ago Auburn did their winter training in LCM for many of the reasons stated in this thread. The women responded well and I think it won the NCAA title that year, but Marsh said the men looked tired all winter and underperformed.
It is easy to overtrain in LCM and it is easy to get into a slow groove and swim in a way that really doesn’t help much in LCM. But certainly there is value in doing it some.