I agree that N-400 is almost a clear cut case, you qualify or you don't. There might be some fringe cases but burden is on the applicant to prove, so they can put newbies on these cases.
When I say the rulers put the rules, I mean the party that is ruling at present dictates where they want to put the money/energy into.
In general, Dems are pro-immigrants and hence you can almost sense they go with higher approvals and lower dillydallying (thats my gut, not backed up with any stats, so please don't shoot me and I am open to data or stats to change my view).