to answer both questions,
The material was not “expected” to remain flexible.
It was not fossilized.
It raises questions about age.
we know that fossilization does NOT take long. it begs the question, How long did it take, how old is this fossil.
Now to question standing evolutionary thought, is un thinkable!
Honestly is needed.
Do you think implying that they found '“highly fibrous,” “flexible,” and elastic bone tissue that “when stretched, returns to its original shape”' is providing that honesty?