Yep, I think its legit concern. In today’s fiat system in the US, any significant income to your bank account, ie if you wanna buy a house, is scrutinized (ie where did you get this from?) and its reasonable to assume that centralized exchange will be forced to do the same. So if you need to sell it on an exchange (finding someone peer-to-peer requires a lot more work and danger to get screwed, especially to normal people who trust the institutions), you will need to prove where you got it from and it will be easier when the institution can prove when you bought it.

Not saying I endorse this, just my attempt to explain.