yep, there's something to that, but if I only train an exercise once a week I lose the groove of the exercise, basically my skill at performing the lift is lessened
I can go 3 or 4 days and keep my groove, but after 7 days or so my skill at the lift lessens
Losing the "skill" of doing a simple movement in seven day does not comport with common sense. Riding a bicycle or driving a stick shift is far more complex but once you learn those skills it stays with you.
Besides, adapting to a movement often triggers the adaptation response. Doing the same exercise week after week, month after month, often is the reason for stagnation.
If you lose fine motor skills in such a short time then it would seem to your body it is encountering a new stress variation and your triceps might respond better to this new adaption response.