I believe that you can "force" your way through basic mechanical practice as a matter of discipline without any ill effects. That's just a matter of building a habit, which the science shows takes anywhere from 2-6 weeks to establish before it stops requiring willpower to get it going. After that, the habit pretty much carries itself on with minimal fuss.
As an example, for much of my adult life I was a martial arts enthusiast before I had to stop studying in 2014 when at 50, my knees were shot after a number of ever increasing knee injuries leading to procedures. What was interesting was that once that habit was broken, I had to establish a new habit of rehab after the last major surgery. None of my previous habits, neither musical or MA habits, carried over into the rehab phase and I had to rebuild those from scratch. Part of those involved walking/running on an elliptical for 30 minutes a day, 6 days a week. It took about a month to establish the habit, but once established, it became the core of a daily 45 workout that I am still doing over 6 years later. I will never again be able to participate in vigorous athletics, but it's still a healthy habit and I make sure to do it 6 days a week unless I have a fever or am literally too sick to do it. 95 days out of a hundred I feel better when I am done than when I started. Those other 5 days are just the cost of doing business, and well worth the trouble.
Musically, there has been a parallel to this in the past few years. Life had gotten very busy with work and family and practice time got relegated to whatever time was left over, usually when I was already very tired. Instead of just not picking up the bass, I built a mechanical practice habit I think of as "
calibration" about 2 1/2 years ago and have been doing it 6 days a week as well. No matter how tired I am, I make myself sit my backside on the bass stool and do this every day, and the habit makes that a lot easier. The deal I made with myself was this: ideally I would use this mechanical practice as a warmup (see linked thread), but if at the end of it I was too burned out to continue, I could stop, knowing that at least I have done something and my body is still calibrated to the instrument.
To finally answer your question above, it absolutely improves function and endurance, allows me to sleep with less guilt/regret, and on those days when I do continue on to creative practice, is a great warmup to get the motor running. I haven't seen a downside.