Headline is rather misleading as neither 1) hitting a $1M in sales or 2) raising $8M in venture funding necessarily means he actually became a millionaire.
The company isn't worth more than $1 million until someone else exchanges shares or money for it for over a million dollars. VC funding does not make someone a millionaire, except in rare cases where founders are allowed to sell shares to 'take money off the table'. VC money is the hope that the company will be worth $X in the future.
A VC investment is literally the exchanging shares for money. No it doesn't make someone liquid. Yes it does set something sorta like a market value, though it's usually really high. In more meaningful terms, that company now has $8 million in cash. There's almost no scenario where it's worth less than $8 million now, because companies at that stage usually have very little debt.
The expectation of funding is that it is spent growing the company (employees, inventory, etc), not immediately paid out to the founders.
Based on that article, we don't actually know if Lee has assets worth $1 million. This is all before even bringing up how liquid he is.
Now we don't know the exact nature of the share distribution, but since this is such a lean company I'm willing to wager that the found is still in the vast majority.