You'd have to ask the mods for details, but I think that it got changed to be in line with the rules, and only block new submissions if the previous one had upvotes or discussions. It might still trigger for a very short time without those, not sure. Especially since in practice there's often multiple URLs for the same story (sometimes even on the same site, with tracking crap in the URL, AMP versions, ...), so it can't be relied on anyways.

With way ranking works, if an initial submission gets no upvotes it's basically necessary to submit it again to give it a chance - of course if it has been submitted a lot and none got traction, submitting yet another one likely isn't useful either.