I have not heard of them, but there certainly are a few regulators sold as MPPT
that are not.
There are also many poor implementations of MPPT
that are not very good.
If going for an MPPT regulator
I would go for a good one like the Outback. If you want a cheap regulator
go for one without MPPT.
The only bargains are some specialized regulators made by small firms for things like the solar
cars. Some of these are very efficient (better than the expensive commercial
products) and are cheap
enough that you can have one controlling each panel .
On a boat MPPT on each panel is better.
I think the conventional approach of a single
MPPT regulator for multiple panels
produces very little advantage on a typical yacht.
A model called “Fat max” looked very promising in this regard, unfortunately it does available at the moment.