Obviously they are not. One has to be pretty unconcerned to pay so little attention as to not realize there are simple solutions. SIMPLE solutions.
The only area of POSSIBLE confusion, "can I register at my school address?" is resolvable with a phone call. This "confusion" can be avoided altogether by realizing that EVERY STATE recognizes students and military to maintain their "home of record" as their legal residence. Do it that way and you avoid any possibility of anyone accusing you of being wrong. How easy is that?
As for absentee votes "not counting" unless the election's close, the same can be said for every individual's vote.
Here's what people mean; and it's an attempt to scare you into thinking people are trying to suppress your vote. If you vote absentee, your ballot is listed and kept aside sealed. You can still show up at your polling place if it turns out you didn't need the absentee ballot, and in most states you are required to do so. If you come in to vote in person, your absentee ballot is marked "VOID" and set aside so you aren't voting twice. This is why they aren't tallied until after the polls close. It's to be positive you aren't coming before they open it.
Now, however your precinct goes, they can't know the outcome of the whole election so your absentee ballot WILL BE TALLIED no matter what. If the final total margin for the entire election is larger than the total number of absentee votes (and it almost always is) there is no point in researching to certify the ballots' validity so they don't and they aren't reported in the final "official" count.