@squitirogloria
You ask "you are in normal bone territory. Is it just from the BHRT and strontium, or other things as well?"

Well, Bone health is a synergistic action. Lots of moving parts that make up how a healthy body makes bone and keeps it healthy. Pharma drugs try to put a stop or a push to parts of that synergistic action.
Supplements, exercise try to meet the needs of the bodies' synergistic bone actions. To basically up everything that the body needs or supply what the body is not getting and allow the body to react. BHRT especially works in this context to provide the hormones needed for an aging body to mimic a younger body and make bone.

Now....consider...

Strontium citrate is a mix of pulling all the levers of normal bone actions in full, not in part like pharma drugs do. It impacts both osteoclasts and osteoblasts using the bodies' own calcium receptors and something which science believes may be a strontium receptor. So taking strontium gives the body something for which it is already set up to receive.

But here is the difference, strontium citrate users take strontium at a therapeutic level, at a drug level. So although the body knows and uses the strontium similar to calcium, if you use strontium citrate you usually take it at a "drug" similar level.

And yes, BHRT plays a role. My endocrinologist explained it this way: "the estrogen drives the calcium and strontium into the bone". But I know from talking to hundreds of strontium users that strontium citrate can work without BHRT.
Whether strontium at a non therapeutic level combined with BHRT would work, I do not know; it would probably depend on the level of osteoporosis.

We need more research, but that is hard to finance for a supplement.

So yes, bone building using supplements which the body already recognizes involves many moving parts, but using strontium citrate at a therapeutic level seems to be able to act on its own to change bone density and fracture risk. (per all the research which I have seen)
https://www.inspire.com/groups/bone-health-and-osteoporosis/discussion/2020-a-review-of-latest-insights-into-the-mechanism-of-action-by-strontium-/