I posted something along these lines a while back, possibly in
@Gamer Pradosh thread.
I don't think it should be linked to attribute or skill increases and decreases but more to do with timing and confidence. Shots and deliveries reduce or increase the timing window or become more effective, as is the case now, with higher confidence. A batsman that is a quick starter should have higher confidence leaps or possibly start with higher confidence but is perhaps more vulnerable to getting out by playing certain shots. They need to be balanced effectively to ensure that certain traits are not overpowered.
For a bowler starting a spell, like a spinner, you could be able to bowl all deliveries but until they are confident it is more difficult to execute variations. An off spinner for example: you have a default timing window for the off spinner, then for the arm ball, top spinner and doosra (in whichever order) as primary variation, secondary variation and unique variation. As the bowler becomes more confident the timing window to execute widens making it easier to bowl the deliveries. Depending on skill level of the bowler the timing window would have a upper and lower limit. So to execute a doosra perfectly with a part time bowler is very difficult even if they are fully confident.