Alright, here's an update on the replacement driver Simon from Convoy sent me free of charge:
He sent two drivers, both look physically undamaged, and both behave exactly the same way as the one in my S9 did. This tells me that the bad LVP is either baked into the design (aka just bad design), or that a whole batch of drivers have a manufacturing defect (such as a different resistor value in a voltage divider or something). They also both charge a bit high (4.25 and 4.26 V). But hey, at least they're consistent I guess.
I'll get back to Simon on aliexpress later tonight, will see what he says. I'll also have a closer look at the driver later to see if maybe I can replace a resistor to make the LVP function properly.