Hello,
I was not able to reproduce the issue.
Product limitation set to "2" for the group "Author", limitation value save and configuration page saved too.
My test vendor is in several groups :
pasteboard.co/J7q7i3p.png
When I try to create a new product, the product limitation check is done and refuse the display of the page
Error
The limitation of 2 products has been reached
Please note that the limitation is check only on "main" product, which do not include "variants" or products waiting for approval.
If you do are using the approval system, the vendor can submit multiple products for approval while he is still under the limit ; since the "waiting approval" products are not counted, you can have the feeling.
Regards,