This can happen in random circumstances. A long time ago Amazon did not allow me to ship to my home address. By trial and error I found out that if I changed a specific o in my address to something else, it suddenly worked. There are no special reserved or offensive words in the address, I've never found out why this was. It had been fixed since.
Also I own a domain name with a catch all email address. If I sign up for websites, I often use the company name in the email adress to track leaks or spam. They sometimes don't allow this.
I only recently switched off the catch-all email configuration. Until then, I did what you did. But over the years, I got an increasingly annoying amount of misdirected email (possibly legitimate business, marketing, and spam) sent to all sorts of usernames, and only landing in my inbox because of the catch-all.
I now just generate masked email addresses with Fastmail. Much less noise now.
company@example.com is too obvious, so I've gotten into using company_jei68@example.com, where jei68 is just me mashing on the keyboard and different every time. Very handy if you have to prove that a particular database got popped.
Also I own a domain name with a catch all email address. If I sign up for websites, I often use the company name in the email adress to track leaks or spam. They sometimes don't allow this.