22, Goal line & Touchlines are all ' Continuous lines ' as shown in Law 1, whereas 10m (5m 15m) is a broken line.
Q? is this significant re: foot over Line principal v ball travelled ?
Yes it is, and you have hit on the reason why it should be treated differently (refer the OP)
A foot touching a touchline, goal-line or the 22m line is easily spotted as touching. A foot between the dashes on the 10m line would require some visual extrapolation by the referee.
The fact is,
the ball must reach the 10m line at kick off/restart. If the kicker, or a team mate catches the ball before it reaches the line, the restart is not valid, even if the catcher is beyond the line
This is similar to the Law regarding a ball thrown in from touch at a line out or quick throw in. It must reach the 5m line (as it happens, also not a solid line), except in this case
no player is allowed to prevent it reaching the line, and even if that player was standing beyond the 5m line, it is not play on!