(thanks for the welcome, btw, though I've been here for a few months)
Yes, it is marketing. No, I don't think it is a ploy (MHC's ridiculous prices notwithstanding). You are saying you don't advertise newsstands as being 1:100 when you sell them, but the empirical evidence is that this is quite a realistic estimate (your argument of "why not 1:50 or 1:250?" can be translated as "nobody knows exactly what it is, so why bother mentioning an estimate?" --well, because estimates are out there for anyone to come up with via eBay (or CGC as well, I suppose) and, yep, ~1:100 is pretty close in many cases, so why are you opposed to people referring to that? I don't think it's false advertising or wishful thinking, the numbers out there support that well.
On your comment about issues that gain in popularity/price and then becoming more available: yes, you are correct for pre-2000s issues and post-2000s direct issues. The main difference between that population and post-2000s (roughly) newsstands is that 1:50 or 1:100 or 1:250 scarcity. The small amounts of newsstands printed post-2000 (inferring from the greatly reduced overall --direct+newsstand-- print volumes compared to pre-2000) mean that there aren't many collectors/hoarders/dealers out there who have those newsstand copies and you only get odd cases every now and then (the Doc Collection is a prime example, as well as 2-3 folks selling only newsstand editions on eBay, so I imagine they are sitting on stock they somehow accumulated via a newsstand store they owned or had access to its supply --but I'm only guessing). Furthermore, newsstand copies have been commanding multiples of direct-prices for at least 6 years now and, if your theory were correct, we would already have seen an influx of newsstand copies due to the higher prices --but we haven't and, on the contrary, that supply has dwindled, especially for 2010-2013 issues. So, respectfully, what you say is not what we've been seeing. I would like it if you were right (so I could get some of the late newsstands I'm missing to fill my collection), but I don't see any way this happens.