The 1:9 is ideal for a 55 gr bullet. The typical .22LR is about a 40 gr bullet. That doesn't require as fast a twist, but 1:12 is probably optimal. 1:16 sounds too low for good stabilization. I tracked down a web page with common twist rates for T/C Encore/Contender barrels. The cite 1:16 for rimfire .22. Faster rates for center fire. See twist rates.
1:12 eh? That could be. We had one of those S&W M&P 22s... looks like an AR, but shoots the .22 rimfire. We read that it had a 1:16” twist and it was very, VERY accurate. Thanks for that link on the twist rates. I’ll look it over. :-)
The 1:16 inch twist in a 22 Long Rifle is excellent. The faster twists in most centerfire rifles are necessary for longer bullets.
The optimum twist for any firearm is the slowest that will just barely stabilize the bullet. Faster rotation simply magnifies a bullet's imperfections and causes inaccuracy.
For a learned dissertation of the subject, read the book, "The bullets flight from powder to target". For a quick and dirty formula to calculate the twist necessary to stabilize a given bullet, Google "Greenhill Formula".