In lowsec, while there is no CONCORD, sentry guns are still active and attack anyone that commits an illegal act in front of them.
Those guns are an active part in pvp play and experienced pvpers often yellow box on gate and station trying to get the other party to shoot first as its better to have the guns assisting you than shooting at you (eg. You’re in a frigate that can’t survive the sentry guns, but want to engage a cruiser). Yellow boxing, particularly on gates, is a regular thing that happens.
A big part of that, is luring the other person into making a mistake. If, while yellow boxed, someone can still safe log, that whole form of play, totally unconcerned with highsec issues at all, will be affected.
Similarly, on the whole “if someone is aligning, they should be nump immune” thing, will also affect lowsec pvp. Bumping on gates is a way that smaller ships (eg. small frigate gang with logistics), can engage much larger targets like battleships. Larger ships often try to burn back to gate and rely on their tank, so bumping is an active part of keeping the target in system, because the aggression timer restricts them being chased through gate.
If a ship can just align back to gate and be bump immune, a whole set of tactics in lowsec pvp will be affected by the change.
Similarly in both lowsec and nullsec, one tactic used by fleets that don’t have a/their dedicated scout with them, is to send a relatively fast ship through the gate to gather intel about the enemy on the other side. They then burn back to gate fast and jump out, so they don’t die. Bumping is a counter to them getting back. If aligning prevents bumping, much safer intel gathering will be the result.
All changes have effects beyond their intent. Unfortunately, few people actually think about the potential negative/other effects of their proposals. They only think about a very small, very focused aspect and forget the larger picture.