I think it's just implying a word for brevity. It's a comparison so the idea is to compare it to the pinnacle.
Fuck works in many cases.
As cold as (ice/fuck)
As hot as (hell/fuck)
As silly as (arseholes/fuck)
The great thing is you don't need to swear - you leave that to the listener. I hate when people write f*ck, f**k, etc. If you're going to swear then fucking swear - don't pull the punch. But this is kinda stealth swearing, and I like that. You get people to think the swearing for you (or not if they're not sweary folk). You're not pretending to swear - you're allowing them to.
On the other hand - maybe I'm wrong. Maybe "funny as" and "sweet as" shouldn't be followed by "fuck" - but that's how I read them.





