" Less in one's control, their parents were financially successful or were in competitive positions"

Yeah that's 50% right there and 'learning strategies' is only a part of it.

The other 'strategy' is 'being rich' or 'connected' or knowing a few arcane insights that do not amount to 'competitive strategies' so much as 'inside knowledge'.

"Long story short: there is absolutely a culture of improvement that is primarily offline and less visible"

Let's not conflate 'climbing the social ladder' with 'improvement'.