Maybe you've had strange customers in your customer list, with cryptic first and last names, and maybe even a lot of them at once.
These are bots that look for vulnerabilities. Mostly they are harmless, but annoying. Nobody wants to have hundreds of bots as customers.
We therefore test customer registration using a stopwatch. Anyone who fills out the form in under 5 seconds is a bot and will be blocked. This does not provide 100% protection, but it should stop most of the bots.
At the same time, it is tested whether there is a URL in the name - another popular trick of the tormentors to bring unauthorised spam or even malware links into the admin area. This is now also prevented.