ANY 1/2" pitch of the correct width will work fine. Obviously SRAM has an incentive to try to convince their customers to spend replacement dough on their own products, but there may also be a legitimate reason for the recommendation. Besides carrying the load, index shift sprocket are shaped to optimize shift characteristics. That means the chains (ideally) should be matched so the plate profiles are the same.
I can't say how much difference the "wrong" chain may make, if any, or whether that difference is meaningful and how much (if any) shifting will be less than optimal, but I expect that it'll be minimal (if at all). in any case, nothing succeeds like success, so stay with what's been working fine for you so far.
FWIW - the flat top chain was designed to increase clearance on the sprocket side and facilitate chain dissengagement when shifting. Based on that logic, it MIGHT actually be more likely to come off the single sprocket than the chain you have now.
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Last edited by FBinNY; 11-10-22 at 03:48 PM.