Provided the land you are selling is yours and there is none that will come later and put pressure on you for selling the land. To me it is the best approach to raise money instead of going to borrow money to invest in bitcoin I will do the same thing if I had land to sell and raise money. Provided that you don't have intention of developing the land in the nearest future, and there is no pressure on you in the place you are living currently. I don't see any reason for keeping lands while the land can give you a reasonable amount to invest in bitcoin. There will always lands to buy when you make enough money.
One interesting point you have made is the point that he is not borrowing to invest on bitcoin from where he would be pressured or expected to pay back with no appealing when there is a time due agreement.
Selling your land to invest on bitcoin do serve as you having your own money to take the risk but also must have had twice thoughts so that you either no begin to panic with the expectation that you will begin to make profits in a short time.
For me any asset that's not providing any immediate use can be disposed and raise money for investment.
At this bottom, please be rethink and check, lands appreciates in matter of time as bitcoin does increase in matter of time so you don't think you are Investing on bitcoin for quick rich.
Besides the appreciation of lands can come quicker than that of bitcoin but the advantage bitcoin has over lands is the high volatility that makes it flexible to skyrocket. But be sure that lands values does not face economy inflation unless at a crisis ground.
I am just to say owning a land is not a waste for it has it side of store or values during inflation but limited to crisis like pandemic while bitcoin as a digital asset can always be set free not being affected by crisis as advantage over landed investment.