I was not aware of twist shifters still existing in SRAM line. Are you sure they are not discontinued? I have 2 kids, plenty of children bikes passing around with twist shifters, and the only ones with SRAM are those 8y old or older... They have discontinued IGH, even though they had the technical lead when they bought SACHS back in the mid 90´s, and they were mostly activated with twist-shifters.
Problem with SRAM is that they have focused so much on the top level (and Campagnolo even more extreme) that there's no entry level bike with their components. Which Shimano, and now Microshift and Sunrace have been quick to use to their advantage. And nobody mounts twist shifters on top level bikes unless personal preference or physical limitations.
Doing a $300 derailleur well is easy. Doing a good $20 derailleur that still works after 20 years is something where Shimano still has the upper hand.
When I look at buying a used bike and it has old grip shifters, I pray I don´t have to swap cables... Such a nightmare job, makes me think they manufactured them to be disposable with each cable change...