I have an original FlexM1 in my P1-R which I can see it but only if I splay my fingers
But my ApexFlex P1-L I cannot, it will depend on your install and anotomy.
I have skinny hands, but others with fatter hands may hide implants better.
If your actual question is, has anybody ever noticed them, the answer is no.
Not at all, its really convenient, I have 3 in close proximity on both hands in P0, P1, P11 and no issues with any.
After install, you may feel itchiness as it heals, and a slightly numb for a while after, but after you are fully healed, you shouldnt even know it is there