The OP forgot to mention 1 critical thing in his opening statement that make a big difference and the brought it up later: “But for folks who may have another way of testing both their room and the speaker, e.g., when there is a lack of flexibility in the placement”.
If your speakers have a specific spot that they have to reside in because of lack of space or WAF, then that changes everything and if this is the case for this install, why not bring this up initially? Why would the OP state positioning the speakers optimally if you can’t?