It is true that the main question in the first post you linked is not "What PCB fab house should I go with?" (shopping question), but rather "How can I check whether a given PCB fab house is reliable enough?" (not shopping question). The mistake OP did was probably ending his post with:
Do you have some good experience with a PCB-company?
which really looks like a typical shopping question.
Simply removing this sentence, in my opinion, brings back the post within the "on-topic" category. There has been a few occasions where I saw similar posts that could be improved to avoid them being mistakenly considered off-topic, and I gave some suggestions in the comments to make the appropriate changes. This post could have benefited from this, I guess OP wasn't lucky enough.
Anyway, when a post starts being in the close queue, even if edits are made that clarify its on-topic status, it typically ends up being closed anyway (that's the way stack exchange works, unfortunately). But it can possibly be fixed now, by removing the offending sentence and voting for re-opening, which I did (I also retargeted the title a bit).
Now, to answer your specific points:
If the question is clearly off-topic from the start (e.g. blatant shopping question) with no hope for on-topic reformulation, there is no reason to give OP more feedback than "Your question is off-topic because [...]", which is what the banner says. So in this case, yes, I just vote to close and move on. I don't think this PCB fab house question falls into this category, however.
I don't see any similarity between this question and the other one. Maybe you want to say that there are some question one might consider not compliant, that gets highly upvoted instead of being closed? Well, this bird powerline question isn't that bad, and I can tell you why it got so many upvotes: Hot Network Questions, as always.
Yes, engineering requires practical solutions. But it doesn't make theory any less relevant, and it doesn't make all practical questions on-topic. Product selection questions were made off-topic, even if they are practical, and are a major part of electrical engineering work. This has been debated to death here in meta, on multiple occasions (I don't personally agree with all the reasons, but this is the consensus we have to conform to on this site).
Indeed, this would have been nice in this particular case where the question was salvageable. Maybe it's going to get fixed.