9050s guy here, all the way. Currently trying the LaBella Deep Talkin's; quite the long break-in before I was happy. To be fair I should have gone heavier, I really like .045-.105s best. I'll probably try the TIs soon, we'll see.
"Grabby" flats at first? Well ... So OK, some chemistry/science to follow: nothing too heady. Go to the next post now if you aren't interested.
Chromes and Cobalts aren't all chromium and cobalt; those are components of certain types of stainless steel. Nickel is another one, but it doesn't sound as exciting and other strings are already called that. The metal may be high in it's namesake, but, well, marketing/niche.
When worked/formed/scraped they form an oxide layer that is tough and not very reactive; it oxidizes either over time exposed to air over a few days, or by being passivated (using an acid to "pickle" them.) That's what makes them "stainless."
When that happens the surface layer is not smooth and shiny like some metals, it looks like a nickel (hence the name of the coin.) It's non-iron rust, basically, which is much better than iron rust because it's protective. So the strings can last a very long time without changing. Eventually.
In addition the layer has a "fluffy" part, just like rust, that wears off over time (like almost a month, depending; I usually get through it in less than a week.) That makes for the grabby feel at first until your fingers polish the surface. It's also why your fingers may have some of the oxide on them initially. And it's also why the tone takes time to come in, as the dullness wears out; you can hear it as well as feel it! With all the surface area of flats it takes some time, whereas for stainless or nickel rounds only the tops of the wrap wear off and do that very quickly, like in the first few minutes of playing, and there's not much surface to grab, anyway.
By the way, it continues to wear very slightly and re-oxidize forever in use. Some folks are sensitive to those oxides, nickel in particular, so you may see something like someone doing bass videos wearing gloves, as an example! Plus that may even explain part of the mysterious bad feeling some folks get when trying flats or even nickel rounds.
OK, sorry, 40 year real-world nuke power plant operator/industrial trainer mode off, carry on...