The little slimline twist mechanisms are hit or miss in my experience. Sometimes they are really tight/sticky, sometimes they are just right, and sometimes they are rather loose. Most of the pens I have turned so far are a slimline of some kind, and I am thinking about moving beyond them. They seem to be more challenging than bigger pens to really get the blanks turned down right (for such a slim pen, there isn't much room for error, and the slightest mistake turning can result in little issues...in relative terms, diameter of the pen wise, not getting the diameter exactly right APPEARS to be larger with slimline than with pens with larger diameters, even if the actual error is exactly the same), and the kits, being so common, don't always have the best parts or mechanisms (goes for pretty much all of them, from Craft Supplies USA, Woodcraft, Rockler, or anywhere online...)
FTR, you can buy packs of those twist mechanisms. If you end up with a slimline that has a too-loose twist, you can usually pull a smoother one with the right feel from a $5 pack of those mechanisms (I'd look around, you can usually find a pack of 10 for around five bucks if you look hard enough.)
I've started buying more larger pen kits, and they just seem to be better overall. Woodriver's Wall Street II and III kits, of which I bought a few today, have twist mechanisms with a little bump and "snap" (soft snap) when they are fully open so they stay open. Most of those kits have fairly consistently smooth twist mechanisms, and I haven't bought one yet that is either too tight/sticky or too loose. Same goes for other kinds of pen kits of similar size, from a range of sources.
I've also gotten hooked on rollerball and fountain pens now. I started turning some of them, and they are so nice! No twist, they have a cap instead, and a lot of those kits have a plastic thread with a plastic protective sheath (to keep from scratching the nib) in the cap...and it just feels SO NICE the way they softly thread together and stop with a soft touch.