I tend to agree. I think this hasn't been tested enough to even begin to assert that Person A's claims are or aren't valid. There may be a lack of evidence, but, as this point in time, it's only for lack of experiments on them.
IMO, the most intellectually honest answer from the "scientific community" right now on this topic is "we don't have sufficient evidence either way (for or against)". We have plenty of anecdotal evidence that drugs can work great wonders for human psychology and just as many that it causes great harm. Maybe both are true and using these drugs requires following a specific procedure to receive the intended benefits.
We may never have a definitive answer, especially since this deals with consciousness -- something that we'd like to believe we understand but don't know the first thing about.
There are people who smoke pot to get high, and there are people who use cannabis to open their minds. That is basically the difference between those it helps and those it harms.
Playing with your mind; going down the rabbit hole... but then you got to get back out.
And if you haven't developed your brain muscle, then it is usually a losing battle.
There are huge piles of similar experiences. Some consider that proof enough. But, since we are talking about personal experiences, it is not something that you can just give to someone who hasn't trod the path. I wish it was as easy as, "here, take this drug," because it really is more about the preparation than the drug.