Contrast:
Pot.3 Fr WR Mark Ryan PP: 57% GS 13/13 Starting WE: 56 +6 WE over season (10%) - 61 thr, 33 catches
Pot. 3 So RB Martin Bailey PP: 43% GS 13/13 Starting WE: 50 +2 WE over season (4%) - 54 thr, 36 catches, 161 carries
Pot 3 Fr OL Matthew Aguilar PP: 42% GS 13/13 Starting WE: 51 +4 WE over season (7.8%)

My RB gets 3x more opportunities with pretty comparable numbers starting numbers (I know higher WE breeds faster growth of WE) otherwise but has lower WE growth than comparable players. Can I conclude that 'touches' really have no influence on work ethic? That Bailey was only +2 is annoying.

"Touches' have not effect on WE. WE is affected by playing and their potential.

Martin Bailey is a sophomore while the other two are freshmen. A sophomore would expect to receive more playing time than a freshman. A freshman's WE would grow more with equal playing time, all other things being similar.

As strieffman said, it depends on how long the player has been on your team, i.e. freshman, soph, etc.

Freshman: If a freshman gets enough playing time to get credits for starts, then his WE will rise significantly. If you do not play a freshman, his WE will not drop, UNLESS YOU PROMISED HIM A FRESHMAN START OR PLAYING TIME.
Soph: If a sophomore gets enough playing time to get credits for starts, his WE will improve some, but not as much as a freshman. If he does not get any playing time, his WE might actually start to decrease slightly. I have seen this a lot lately. If my sophs don't get playing time, their WE will decrease 2-3 points over the season. And if you promised the player a Soph start, you better stick to your promise.
Junior: He expects significant playing time. If he starts every game, his WE might rise 1-2 points over the season. But if he gets little playing time, his WE will start to drop significantly. And if he is really ******, he might leave your team before his senior year.
Senior: By the time they are seniors, change in WE is meaningless. They are who they are. No big changes in their ratings at this point.