I am a mathematician, and I always ignore requests to submit papers using a certain LaTeX template, or using any other journal-specific formatting. Judging by the papers I get to review, so do most other mathematicians.
Once (for a Springer journal) I got called out by their editorial staff, and told I had to follow their dumb rules. So I did. But I would never do this preemptively.
Publishers charge thousands of dollars for a subscription to a single journal. If they want their papers formatted in a certain way, then they can employ staff to do that work themselves. If any for-profit journal tries to insist that authors do lots of reformatting work before even submitting, I will never submit to or review for them again.
Once (for a Springer journal) I got called out by their editorial staff, and told I had to follow their dumb rules. So I did. But I would never do this preemptively.
Publishers charge thousands of dollars for a subscription to a single journal. If they want their papers formatted in a certain way, then they can employ staff to do that work themselves. If any for-profit journal tries to insist that authors do lots of reformatting work before even submitting, I will never submit to or review for them again.