I have one like that. I have the email first.last@gmail.com, and I have a
very uncommon last name. Lo and behold, Google let some dude in Australia who happens to share my name sign up with firstlast@gmail.com. According to the docs the two should be equivalent, so they shouldn't have let him sign up, but they did... and now I get his email all the time. I have gotten job offers, bills from medical offices, even one follow up email from his therapist. And lots and lots of ads, of course. I have tried to let people know (when it's a real person contacting me) to let this guy know about the email situation, but either they don't reach out to him or he doesn't care. At this point I just delete all the emails meant for him without reading them, and figure if he misses out on a job offer or something... I tried my best.
Still, bizarre that the situation was allowed to occur in the first place by Google. Clearly they need to beef up their account creation checks a bit.