the more burn the better... and if it was my sand I do believe it would get a short vinegar soak too. My peroxide would be the 35% from nature store on 82nd and Quaker or just a few cheap brown bottles all dumped in the rinsed sand that was already cleaned. Left a few hrs.
Pre tested in a side dish for dissolution time... one can control the ability to burn just the top layer off the sand where supposedly the phosphate from prior use has an affinity for the arrangement of the calcium carbonate that makes up the bulk of substrate exterior
it's true that tank keepers who had live rock in a sustained eutrophic tank muriatic acid burn the rock... same here but on a micro level and with weaker acid. Most wouldn't take the time to prep old sand but what else would be as fun
Those rocks you made are really well bio planned I can attest really they've cooked ideally. Full of bac.
The tank can be setup and be known to be free of literally all obligate hitchhiker maladies for both fish and substrate the way you've guided the curing rock.
But the non obligate hitchhikers...those that get around without our help, the same routine runs the new rock when it's back under lighting and nutrient: frag trades even with good intent and pre scrape cleansing will bring in new battles, attack with metal
Or, find a grazer balance and by all means use any doser that works. These rocks won't be immune to invasion, they're just the best possible playing field in your favor. Guaranteed w holler soon after wk next day or two and quit being antisocial and come look at it lol

the rocks will carry all initial bioloading the sand won't matter if it's burned new or cycled by itself.