There is definitely a bit of a trend towards longer barrels. I think many people will stay a little shorter as guys want to use suppressors more frequently than with centrefire.
I'm guessing most people are doing it for balance reasons, now that 22 PRS is basically the same as centrefire PRS (barricade bench rest) there's zero reason to not go as long and heavy as possible for the same balance reasons.
There's been daily streams of the international rimfire championship in Italy these past few days.
www.snipershide.com
Theres some stats here from the 2023 IPRF world champs, you can see 20" is by far the most common barrel length, but you'll also see that the majority of people were shooting factory rifles and I'm guessing 90+% of these will have 20" barrels. There's quite a few 18" barrels there too but I bet almost all of them were on Begara B14Rs.
Around 40% are longer than 20" and I imagine almost everyone outside of real facotry rifles (T1x, CZ. RPR etc and opposed to pretend factory like the MPA/Vudoo rifles) are all in this 20"+ group.