They aren't just selling standard keys that will give you access on release though, they're selling virtual currency and release state override keys. The latter practice at the very least is
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.
I agree with you that Valve won't do anything as they selectively enforce their own rules, I suspect on the logic that it's a pain to enforce and they'd rather have a subset of devs freeloading than drive any to competing stores, but I definitely think that they
should enforce rules like this. As well as others like their false marketing requirements which extend to third-party sites.
At the moment Valve essentially let devs do an end run around those restrictive terms, so long as they don't actually release on steam, and more than a few devs (mostly hailing from Patreon) are definitely starting to abuse it.