A few barely-related points:
1) Aircraft
One of the biggest impacts of the PH attack was the neutralization of the USAAF in the Pacific (well, that and the calamity of the FEAF a few hours later). The loss of hundreds of planes (including IIRC all the medium bombers) is an enormous advantage to Japan, because those are the forces which are (relatively) easily deployable. Without the attacks on the PH airfields, at least some of those aircraft could have been diverted to Wake or the Philippines. Instead, it was left to the navy and marines to manage the air war alone for some months.
Even if there is no fleet at PH, the possibility of destroying the airforce-in-being makes it a valuable target; how much of the air presence on Dec 7th was there because the Pacific Fleet was there as well?
2) Japanese doctrine
Pearl was attacked to sink the US fleet, because the premise (wrongly, but there you go) on which the southern strategy rested was that the destruction of the in-theater force would lead to a capitulation by FDR, and (correctly) that the chance for such a victory was slipping away after the Vinson-Walsh Act set out to pay for a really really big navy.
It's pretty much a Mahanian Decisive Battle with some clever bells and whistles tacked on. The IJN battle line existed to sink the USN battle line - preferably after a lot of torpedoes (from both land-based and carrier aircraft, submarines, and destroyers-at-night) had whittled it down a bit.
If the fleet's not at Pearl and thus not vulnerable to the post-Taranto in-port carrier strike, the IJN endgame is still going to be based around it's prior doctrine of getting the USN to sail all the way to the PI, being torpedoed all the way, until what's left meets Yamato et al and makes a new set of reefs there.
That points to the IJN strategy not just being to neutralize the PI as the source of a threat to the SLOC to the DEI, but also to take all the islands they can reach (Wake, Midway, plus the southern ones like Rabaul) in order to provide bases for non-capital unit forces and similarly to deny the US bases for land-based air cover for the Pacific Fleet battle line.
3) PI response.
MacArthur is in command of the US presence. I cannot imagine his formidable political acumen being turned towards any end other than to ensure that any Japanese attack on the Philippines is turned into an career-enhancing opportunity for Mac - which means having, and winning, a short, victorious war, preferably with pithy quotes, good newsreel footage, and some nice live broadcasts with Edward Murrow on the way to the White House.