That's a good point about why would anyone want to truncate a table within a transaction to begin with. It's not likely - and like I said at the outset, it's quite esoteric and not in the mainstream.
More than anything else, it's information about what SQL Server tracks in the txaction log.
The path of learning has many forks in the road, and one little path is debunking myths. SQL Server certainly has a few myths - this is one of them, correlated subqueries is another, table variables always being faster than temp tables another, etc.
