Does that mean that even in Blue Vortex Mitsuki gets 1000x faster when he uses his Sage Transformation?
Well... yes, because his scaling doesn't change. In TBV he'd be MHS+, Rel with ST (he doesn't have any feats that upgrade him, of course with time that'll change.).
Whether you want to word it like that or simply take the feat as it is in the manga is up to you because I can claim the same think for any other amp.
One of the ways Haki works is that it enhances your senses allowing you to react to things faster than you normally can.
Since you're arguing it'd be some type of multiplier since Sanji "scales" above Aisa's potency, it'd be something like this: Aisa would be something like Below Average Human level, MHS+ with Haki. As you imply, Sanji would scale above this feat in reactions as his Haki is superior to Aisa's. So Sanji's speed would be something like Relativistic+, MFTL with Haki (Should scale above Aisa's proficiency in Haki). This would be the justification.
But obviously that's not how that works in the verse, nobody in the verse currently has reactions that span to MFTL, or even higher, as characters currently are now FTL+, and their Haki should scale above Aisa. But for some reason it's not on their profile because... you guys decided to put it on the Haki page?
Because according to the Haki page, if one is a higher level in Haki advancement than the other, then they should scale to their feats.
Another example, we have characters like
Gedatsu and
Katakuri, who both have higher with Haki on their profiles, which is perfectly fine. But they both, according to you, should scale above Aisa in Haki potency, which would also include reactions. Yet none of their profiles incorporate that logic because it's not a multiplier, yet you're acting like it is.
Yes, Haki increases their reactions by alot, but you saying that Sanji would scale above Aisa's feat as if it's a multiplier, yet not only does his profile not show how much faster his reactions would be, yet OTHER profiles with Haki say otherwise, is just wrong.
Like I could literally make the same argument in the Naruto franchise and say something like (goons use this unironically): "KN0 allowed Naruto to go from Subsonic to MHS+ (Mach 8000+), and Sage Mode is a superior form to KN0, therefore it offers a superior speed amp". Which is obviously a stupid take, but that's essentially what's being argued here with Haki.