After some testing, it appears that the bosses are faster? Not sure on that, but my times would tell that it won't affect too much, possibly even positively.
And now I'm total awe of how was that Spoiled Rotten times done? I managed to kill him off in 14 second (Just enough at S-Hard) but these times beat it by 3-4 more seconds?
Also I have few SMG2 times, but those are pretty much what I got on my second time. I did get an loads better time at Yoshi Star Galaxy Star 2 (Did that cause on my run, I managed to get some 50ish Star Bits on the way for the last hungry Luma I'm missing). I have to experiment with Infinite Fluttering to use the neat trick that drops the time to around 1,10 I think.