Some of the negative amazon reviews are fairly scary, such as the one that failed with internal arc/flash when turned on; another received with corrosion, etc.
I haven't looked at the other sites it's sold on to see how bad the problems with those.
It does not have a way to set a specific current limit (just low medium or high, however much those happen to be), so it can damage batteries (cells and/or BMS) by charging at too high a current. Unless you have a very large pack that can handle high charging currents, you could set your pack (and bike) on fire, if your BMS doesn't protect against charging overcurrent (most don't). For instance, there's not many 36v ebike packs that could handle 12A charge current; most of the 48v ones wouldn't handle 10A, etc. Most of them would be doing good to handle 2-3A of charge current, especially as they age.
It does not say what "low, medium, or high" are, not even as a proportion of the "max" current, and it says specifically there isn't a way to set an actual current. So you sets your knobs and you takes your chances.
The ad's pictures (the large one in your post) state chemistry specifically only lead types. It says that it has has voltages compatible with various common ebike packs, but it does not have any way to set it to a specific chemistry (and there's no way it could know or detect this on it's own), so if it is trying to charge whatever pack is connected as if it was some other kind of pack, it could damage the pack (or start a fire).
It's "4 stage" charging (that you can't change) first "pulses" the current (in what way and by how much it does not say, which in itself is dangerous), then at some unstated point it changes to CC mode, then CV mode, then something it calls "recharging", which does not appear to be an actual mode--it would just be responding to a BMS that's in balancing mode (turning it's input on and off as needed, disconnecting and reconnecting the charger).
I don't think I'd want to use this thing.
