Validation correspond to a single inference pass in neural network terms. (which is fast)
Mining is much harder and involves millions or more of inferences passes (depending on difficulty).
Reason is that inference pass can't be easily reversed (mining problem corresponds to a ILP, integer linear programming problem).
More technical details about the pow is explained on this page: https://github.com/nf-dj/robocoin/blob/main/tens_pow.md.

This pow doesn't imply there is more data on the blockchain (there is no more vast amount of data on chain than for btc).
Reason is because the matrix weights used for mining are derived from the block header using chacha20.
(so only block header is on chain, like for btc, not the full matrix weights used for inference).
Let me know if need more clarification, thanks.