Gently, I have been reading and listening to very different perspectives on protein in relation to bone loss and fracture risk than what you are describing. What I have gathered is that:
1. Higher protein intake than the suggested RDA of .8 grams per kilogram of bodyweight is not detrimental to bone density and probably improves it.
2. Higher protein intake is essential for preventing sarcopenia which is a key factor in fracturing due to muscle loss contributing to balance problems and falls and being unable to catch yourself if you do fall.
3. 25 grams of protein in a meal is nowhere near the max that adults can utilize. Donald Layman a noted protein researcher says that somewhere around 30 grams is needed at a meal for skeletal muscle protein synthesis to occur.
4. "Extra protein" is not stored as fat.
5. The paper you link to does not support what you are saying. In fact the thrust of the paper is that it appears more protein is needed especially in older adults for better bone health. The highlighted quote that I see via your link is confusing due to the way it is written. On careful rereading I see the quote means the opposite of what it might appear to mean. Both pieces of the quote do in fact indicate improved bone density with protein levels higher than the usual .8 gm.
6. In the conclusion to the paper you link there is a single sentence that clarifies what the author is saying: "contrary to the longstanding hypothesis, fairly compelling evidence to date suggests that higher intakes of dietary protein do not have any detrimental effect on bone and likely pose a beneficial effect.".

Most of what I've said above is my take on interviews with Donald Layman who seems to be a real expert in the area. It's easy to just search on him and find his website and youtube interviews and so on. Dr. Gabrielle Lyon is an MD who has studied with Layman and emphasizes protein in her practice and her talks are also readily available on the internet.
Hope this is of use.