Respawning destroyed bases

You can't actually land in territory controlled by any other alliance, human or computer controlled. You can land in close proximity which isn't the same.

I know that dude, just curious as to why , it happens on a sector jump so why not after the bases are destroyed, very few enemies will leave you a base to dig a path as They destroy all bases in range

It only happens on a sector jump to avoid you being thrown to the edge of the world as happened when they first introduced the re-spawning.

still not an answer

"sector jump" is an exception to the rule, precisely for the reason explained to you. You cannot move into enemy territory, it's owned and controlled by the enemy.