Blues have stated it on several occasions. You're attempting to trade an account. There's really no point arguing semantics. It's not like it was only meant to cover account for account trading *only* or something of the sort. Account trading/selling is A) not allowed by most services and B) too scam sensitive, hence they're not allowing it.
Look, I found no posts stating that "trading steam account" is prohibited here and I am doing it only because I leave steam, so I am not into "trading accounts" either. If blues ask me to do it, I will remove the post - its just exactly that I expect people here to be much more trustable trade partners, than a random buyer on some 3rd party site that does this daily, so better suited for this one-time migration.