Yes, simple templates like celestial explicitly say "quick and rebuild rules are the same".
On contrary. advanced does have a separate rebuild entry.
Even if you know that animal int is capped to 2 and ignore the wisdom and charisma issue - a heavy horse should not be more dextrous than a a light one. Also, a light horse should be quicker than a heavy one.
Neither is adressed.
Ranger characters I've been playing used to ride light horses so they could use the higher speed for scouting, while the heavy horses of other characters used to carry barding and serve in melee battle.
Now, as things are, no character with any sense would use a light horse.
If there is a bug, fine, such things happen and can be corrected.
To defend a bug by declaring it not to be a bug just because it's been around for a while does not make any sense.
So please let's start and upload a V1.1 errata for the bestiary second printing.