Unfortunately, if a software has a problem with too much UI clutter, probably the worst way to go about it is to add even more UI elements to solve the problem of having too many UI elements. Especially if you default to showing more UI clutter, and hide the option to show less UI clutter in a place where user is almost never going to look.
But honestly, this is not just you. This seems to be a common problem of almost everyone. People just can’t help themselves from adding more buttons. So of course, the first impulsive idea to solve the problem of having too many buttons is “Hey, let’s add a button for that!” 
Having option to do same thing at two separate places (It says all the functionalities will be still available in the addon preferences) is unfortunately a failure of UI design.
If the panel can be safely hidden without losing any functionality, then there’s just no justification for the panel to exist in the first place. My point here is that if you make a compromise in the execution of UI simplification, the end outcome can actually end up worse than the state prior to the attempt.
On a different note:
I know UVPackmaster is just a packer. The way I use it (but I am likely not alone) is that I use Blender’s Smart UV Project operator a lot and then use UVPackmaster to pack the result. The problem with the Smart UV Project operator is that it’s insanely slow. It can take up to several hours to unwrap mesh that has over 1M poly, depending on the complexity of the shape.
It’s not because the Auto UV step is slow, but because the built in packer in Blender is slow, and Smart UV Project makes the packing step mandatory, even though the poor pack which took Blender hours to calculate will be discarded immediately, to be replaced by much better pack from UVPackmaster which is done in fraction of time. It’s really painful to wait for Smart UV project operation where the actual smart UV takes like a minute, and the packing takes like 70 minutes.
So this got me thinking if it would be possible for UVPackmaster to have it’s own Smart UV Project operator which just breaks complex meshes into packable, non overlapping UV islands based on specified angle threshold, which doesn’t run Blender’s super slow packer afterwards, so it could be used directly with UVPackmaster without having to wait several hours first. It would make UVPackmaster dip a little into unwrapping territory, but I think it would really pay off in this case.