It's not comparable. If we question the indigenous status of Philistines why not question the indigenous status of the ancient Chinese or Assyrians or whoever else.
Because there is both material and textual evidence of an eastward migration from either Cyprus/Cilicia or the Aegean, probably from both towards the Levant, this view is supported by the majority of archaeologists, the Peleset only start being recorded with the migration of the sea peoples and their failed invasion of Egypt, when the Peleset are listed numerous times among other invading sea peoples' tribes.
Before then, they were unkown in the Levant, they weren't present in any Egyptian or Near Eastern document, they only start appearing in record after the sea peoples' invasion, which is both reported by textual (Egptian record most of all but also some Ugaritic and Hittitie ones) and material evidence: massive amounts of Aegean and Cypriot pottery in the Levant, especially in the Philistine pentapoleis, Philistine city being re-built in Aegean/Cypriot fashion, Philistine burials being oval pits like Cypriot ones, Philistines using Cypro Minoan script, bringing Aegean features and practice like Aegean hearths, European breed pigs, Philistines being armed exactly like the contemporary Cypriot warrior depictions, the list is long, there is massive evidence for a westward migration from Cyprus and the Aegean to the Levant, the Philistines were not native to it, it's difficult to say where they were from: Cyprus probably, but maybe they were mixed Cypro/Aegean, to what extent were they mixed? This is impossible to tell, what is certain is that they came from the west, by the time of the war against the Hebrews they were mixed with the native Canaanite of course.
The fact that they were allied to other sea peoples, who were notoriously a confederation of many different ethnic groups, makes it hard to establish what ethnicity they were exactly.