I don’t think there’s any reason to doubt it. Underneath all the posturing, Phil actually is aware of his own inadequacy, but he thinks no one else can see it. He’s genuinely ashamed of being a mong, so when he inadvertently reveals that aspect of himself (or at least, when he’s made aware he’s done so), damage control kicks in. When we laughed at his FAS eyes, he started wearing shades. When we laughed at him flailing like a spastic on Tiktok, he made it private. And when we pointed out that his bouncing and squeaking just looked like he was fapping, he took that down.
As an autist with no theory of mind, he often doesn’t realise how ridiculous he looks until it’s pointed out to him. I’d imagine he’s very frustrated that people always see through his act.