Bot subscribers even with double opt-in?

All my email signup forms (via MailerLite Classic) use double opt-in to discourage bot signups. However, in the last few weeks, I’ve had about a half dozen new subscribers with reasonably normal-looking email addresses, usually from the UK or Australia, whose first and last name fields are filled out with the same sort of random letter strings I usually see bots enter in fields they don’t know how to handle. All these subscribers have apparently confirmed their email address in the double opt-in confirmation process, but none of my sent emails have been opened.

Is it possible for a bot to get through double opt-in? Is there some extra precaution I should take other than unsubscribing these signups when I see them? Or are these legitimate subscribers despite the weirdness of what they’ve put in the form?