“The lack of preserved bones within the 15 inhumations...”
“On the other hand, fortunately, cremations are mostly well-preserved.”
“A total of 1,689 cremains were dated and studied...”
They seem to have gotten a lot or relatively detailed information from cremains...bodies that were burned to ash.
Ancient cremation was considerably less efficient than than the gas-fired brick oven modern variety. Most of the bone would have survived intact and was broken up to fit in a rather large urn or pot. Smaller bones and teeth might have remained intact. Modern cremains are run through a grinder.