I think it’s because this sudden proposal is just a pilot study; a steady flow of limited money doesn’t need to be diverted for a temporary experiment like this. The 8 bus expansion, on the other hand, is locally-funded but isn’t budgeted to start until FY2026. What’s the harm in trying something new while we wait?
Besides, Raleigh doesn’t have limited-stop buses that stays within its own city’s boundary (and the closest non-GoTriangle bus like that is Chapel Hill’s FCX, which is one of its most popular routes). Like the summary Francisco copy-pasted from implies, this could also give useful data to argue for even more frequent buses when the 8 bus upgrades come and/or strengthen the study for extending BRT to Midtown.