This is such a weird comment to make: these are companies that can quite literally (and quite often) let you go for any reason at all (if you live in an at-will-employment state). I've done this exact thing before, and I've also resigned without 2 weeks notice to chase greener pastures. Business decisions should always be purely transactional and borne out of your own interest. Anything else is self-sabotage.
Companies sure as shit don't care about you, and you caring about them gives them a leg up, not you.
Most of the time when people do this, they're open to accepting an offer if it turned out to be really great. They just know that such an offer from a particular company is really unlikely.
I don't see a big problem with it. While it may 'waste' some time on the company's part, it also sends a signal of, "hey, you could get some of these really high quality engineers if you were willing to [pay more/offer more vacation/offer remote work/etc.]".
Now, if you're unwilling to accept an offer from a particular company even if their terms blow you away, then yeah, that's a dick move.
This is exactly what I've done the last few interview cycles I went through. For me, my screening interview was with a company that had a tone of public problems with treatment of female engineers and fired the ceo soon after. But they had some good engineers too. I interviewed with them and it was a mess, but I did get good experience. I thought I failed, they never told me, then 6 months later tried to get me to come do a full loop.
I think it's a smart strategy to pick 1 or 2 companies you'd never want to work out, including for low pay, and do your practice there. You should tell them if you pass why you don't want to come there, including for the low pay.
What a shitty thing to do.