I think these accomplishments posts really do not have any form of good intentions like you've said. They could be false, well they're mostly false. Sometimes you read someone's stuff talking about how they've done so much and only within such a limited timeframe. Of course they could be false, but sometimes we don't consider the falsehood most of the time.
The readers just wishes that they could be like these people without even considering whether the poster was lying
Yes, our brains completely bypass that process that it could be false. Arguably, most posts like that are just seeking external validation for something they wished to achieve :)