I took a USAC course on altitude training a few years ago. I wanted to get the "facts" on what works and what does not. Like everything in sports, results are an individual response. Some athletes get better with altitude training, some stay the same and some get worse. The key metric for sea level athletes going to altitude is the effect is the worse on the 3rd day. The normalized general response curve is that athletes start to respond on day 7. It takes 21 days for acclimation.
Athletes at altitude lose VO2 throughput and muscle mass versus sea level. Therefore, the concept of sleep high and train low is the optimal way assuming a generalized response. If one trains hard a sea level, VO2 throughput and strength are maintained while spending most of ones time at altitude invokes a systemic response increasing the ability to transport and consume O2 at altitude.
In general, tents do not work because one does not spend enough time in it. 14 hours plus is the bogey each day not just sleeping. But maybe sleeping 8 hours in a tent provides some level of acclimation.
And assuming altitude acclimation and training works, there is a protocol for when to do it and there are specific spots globally that are considered perfect for getting results. So doing an actual attitude session prepping for an event is hard to do. Everything that is offered that is not actual time in the mountains for a longer period of time will have very mixed results...if any.