If that entire $100k was accrued that year. Presumably something was paid to get the BTC, which would decrease the gain commensurately.
I was going to mention this but it muddies the waters of the real issue.
Why is one cashing out $100k unless they are up like 5x or 10x?
The principal amount becomes irrelevant in these situations.
Considering our position within the 4-year cycle it makes sense to ignore the principal.
The subject of taxes is always muddy water, because it's theft and that bit is necessarily obscured by the scammers, otherwise none of us would pay them.
Oh look an actually "inconvenient truth"