Not being in a new hire drop doesn't really mean it's senior or not. There could be 100 positions available and the company isn't offering any of them to new hires yet due to their priorities. I'm not sure how it works now, but they used to only offer as many positions as were in each class and determined what those would be. If they offer a larger pool now, it could also be that no one is asking for it.

An important thing if the base you want isn't in a drop is to try to get the aircraft that gets you there quickest. If your goal is to get there before anything else. I believe a few also used the new A320 category in SEA to jump types for that reason as well.