Perhaps he is demonstrating that this type of behavior is not wanted. Was there a bug report or jira issue? If not, why are you using company resources on pet projects? I believe this is what he is telling you.

You see that other devs have already reviewed the changes as a good thing. In my opinion this is the kiss of death for your case. Not only are you working on un-prioritized work but now others are as well.

Work on stuff that has been prioritized. Don't get side tracked on work that has not been prioritized. If you believe it is important work, submit a bug report or feature request and get it prioritized. Then you can legit fix it and get it folded in.

I know it seems petty, and I have been guilty of 'drive by refactoring" when I was a junior dev so I understand the temptation to "fix things".

This "bug" is a violation of the Equality Act, and so can have legal consequence if a customer reports it.

This is the type of issues you want to fix before are reported, not after.

It's like waiting for someone to die before adding a zebra crossing.

So, you did not submit a bug or an enhancement request I take it. You unilaterally decided that your code change was more important than the work assigned to you by your company.

If it was/is that important then you can create a ticket right?

the ticket exists and has been reviewed by a Product Owner, however, the other dev doesn't accept it because it's not submitted by a customer