SERVER-109460 did this primary-driven index builds. We should ideally do this for hybrid index builds as well eventually to keep things consistent and simple. There are a few TODOs in the code for this ticket that highlight complexity we can address as part of this work.

We attempted it previously once, but that caused BF-38757. I proposed changing the perf workload to avoid some of the false positives. If PERF-7099 has been fixed, the perf regression "should not" appear again.

Another concern Louis raised here with this is that we we might end up holding the exclusive lock during index build setup a little longer. As part of this ticket, we want to assess how critical this concern is. Given the number of HELP tickets we get due to the complexity of index builds, it should not be hard to justify accepting this cost.

While this ticket does not strictly belong in SPM-4215, it would be nice to take care of it as part of this epic.