I am well aware of that feature gmail has and have abused it in the past with many websites, but the parent said that some SaaS platforms block gmail altogether. It seems like a shoddy fix if you can get a really cheap domain and essentially do the same to register accounts.
Yeah, its like putting extra locks on the front door while the back door is wide open. However, most people would try the front door first.
A lot of domains have that feature btw. Gmail's specific feature is with the dots functioning as catch-all [1] (though Facebook apparently has the very same feature).
