So any time there isn't a percentage next to a position group, both positions get 100% training, correct?
Correct. However how much that 100% actually is in terms of how much the skill will grow depends on a number of variables.
This past week almost all players popped......does elastic effect still occur for two position, 100% training?
Yes elastic effect is so called because the skills you are training (both primary and secondary training) are affected by the other skills. The effect can be positive or negative.