True , I would have made money but not almost double . The simple reason is that once sold , approx 38 percent of the profit goes towards taxes , so when you buy back in you are not doubling your amount of bitcoin in this scenario but you are increasing your bitcoin stash, true.
Besides, your scenario implies you know the tops and the bottoms of a trading period. If you are capable of doing that on a consistent basis, then why don’t you set up a self directed (self managed) 401k( I know you like those) and swing trade your way to easy money ?