No, you are not wrong. Half-Life 2 run on Android phones, but not via PPSSPP . The confusion stems from the fact that people often search for "PSP emulator for Android" and then "Half-Life 2" in the same breath.
If you have a specific file or video claiming to be HL2 on PPSSPP, it's .
Developers have created unofficial native ports for Android (using the Source engine) that run Half-Life 2
Search GitHub for "Nillerusr Source Engine Android" (or look for "srceng-android"). Download the latest hl2.apk .