Overall, keeping tossing arm up for too long is a spread mistake
That is true. Trying to leep the toss arm while you are driving at the ball or trying to do shoulder over shoulder only prevents the trunk from adding power and that is a mistake. I like this guys take on that particular aspect and it is something I am familiar with:
However that's not what I'm talking about since keeping the tossing arm up for too long is possibly worse. There is a relatively small window among ATP servers where the toss arm begins to drop relative to the positon of the racquet (with some variation, but most of that variation is when the toss arm stays up higher for longer as the racquet goes into the drop, and not the other way around - Federer, Zverev, & Rune for example).
Let's put it this way - you won't find many, if any, ATP players with a tossing arm position like the image I posted. I would say Taylor Fritz drops his arm earlier than anyone else I'm aware of and he is known for doing that (partly because he has a late entry into the classic trophy position, as did Roddick). However, other players using that method like Zverev and Sinner still keep their tossing arm up and it stays up for several frames after their head begins to rise as the racquet enters the drop. That's not necessary either and close to impossible for me, and Imo a good reference is that the toss arm and the racquet drop in unison or close to parallel. That is what I would be aiming for and it won't take much to change.
I speak from experience as someone who used to have almost exactly the same problem, and addressing some other technical areas actually corrected that for me, but nonetheless it was a small issue for the reasons I outlined.
@JoshXXX, you may not consider it a problem in which case that's fine and you are good to go, but I would encourage you to take a look at this video.
And compare the timing to when you drop your arm. I already did several for you (including Thiem above).
Skeletal analysis - Roddick in yellow, Murray in white.
And yours again:
Not tragic by any stretch, and Thiem above looks like a good position to aim for. That's my take anyway, and you are free to take it or leave it!