I have nothing against stubbing in general if required for authors to publish their books, personal hate for Amazon specifically aside, and don't begrudge authors monetising their work. I don't think stubbed series should be banned from Scribble Hub as existing readers keeping up with the current releases would be shafted.
That said, if I can't even read the first volume / book here, I want to be able to easily spot and avoid such series. I don't want to read 3-5 chapters then get hit with a 200+ gap.
Especially as plenty of authors on SH don't number their chapters for some reason, so it can be impossible to spot just by looking at the ToC.
Bit of a tangent, but I don't even understand the business sense behind this. Surely Amazon would get more KU subscribers and authors would get more paying readers if people could at least get started with the series properly with the first book in full before hitting the paywall?
Some sort of obvious flag put in the title or before the synopsis by the system would be great, not leaving it to authors where and how (or if) to state it, especially with the info panel being hidden so far down on mobile. And make it a violation of the rules for authors to not disclose stubbing in order to not get the flag on their work.