No. I tried the STK-S6 in the neck position along with an SSL-1 in the middle with an auto-split wiring for notch position, volume balanced well and I liked the quack. I have read the potential problem with duckbuckers and vintage rails is they are really low output but on the other hand it is used as part of the everything axe with single coil sized humbuckers so go figure.
About the treble, I tried it only with 250K pots. It has less treble then an SSL-1 but it is punchier which IMHO makes it a really good candidate for neck in HSS configurations. So it does not sound like an SSL-1 but it is still a Straty sound, I even liked it better than the SSL-6 which sounds great in Charvel demos of DK22 but for some reason in my Strat the SSL-6 was too bassy in the neck while the STK-S6 was much better for my taste.
Edit: The STK-S6 is no longer in the neck of my Strat, I am moving it to the bridge position and putting another SSL-1 for the neck. For a more vintage sound noiseless I would try the STK-S4n, sounds great in the demos but it will have a bit less output and that may be a good thing about the volume balance concern with the Duckbucker.