Only if they proceed AND websites enforce it. The last reply I read from the Googler that was part of the draft spec said they were building in a guardrail that prevents sites from outright blocking non-compliant clients without also blocking a not insignificant portion of their desired userbase.
To me, it sounded like they'd just randomly not send the DRM information sometimes. So, the fix for web sites would be to tell the user to reload until the information is passed along.
That's pretty terrible UX, though. I think it's more likely that websites will continue integrating a CAPTCHA service and that service will simply try to short-circuit its decision by asking for attestation. If none is given the user gets to click on pictures of street lights.
You seem to be more worried about UX than those sites. At least in the EU, the user has to click through a multi-step wizard about cookie stuff to get to any content on every site these days.
This wizard is not mandated by law, but these sites choose to use it anyways, just to squeeze a bit more money out of their visitors.
The devs responsible for this say their goal is to detect bots, but make sure it doesn't harm people not using this tech. I'm actually inclined to be believe them. The problem is that those guardrails could turn out to be ineffective, or Google could decide to just disable them at some point.