Recapturing the phillipines was a personal hobby-horse of MacArthur, as he had grown up there and had promised, "I shall return" while fleeing to Australia.
The original battle plan called for island-hopping which would simply bypass the Philippines. If anything prolonged the war, it was MacArthur's insistance on dealing with the Japanese in the Philippines first.
You are absolutely right that POW and Filipinos (civilians and rebels) were suffering greatly under Japanese rule. And both are eternally grateful that the Philippines was given priority.
But that oppression was over once the Japanese were cornered in dozens of government and cultural buildings. Waiting at that point would not have required many US soldiers (and many Filipino would have gladly volunteered to assist) to enforce the confinement of the relatively few remaining Japanese soldiers.
The Bushido Code also include hari kiri. Already several companies had killed themsleves en masse . Guresome as that "surrender" is, it at least spared the buildings in which it occurred. And we are talking about much more than just edifices. For example, the National Archive was bombed and burnt out. There a virtually no official documents (birth registries, etc.) in the Philippines today that date back to before 1945.