Mary H. Schweitzer, the scientist behind this, has no problems believing it is millions of years old - she is just interested in how well preserved it is in that one can detect cellular structure and even some reactivity (antibody binding IIRC) to heme and collagen.
I thought it was a fascinating discovery. I’m less surprised than most other people perhaps because of the work I had seen about the survivability of living organisms and organic material over past decaddees of experience. I had the privilege of handling one of the Apollo 11 Lunar rock samples in 1971 at a conference attended by a number of the NASA scientists engaged in related research. One oncerns they were discussing at our conference was the problems associated with distinguishing extraterrestrial samples contaminated with biological contaminants from Earth versus exobiological organisms not contaminated by biological organisms from Earth. This conference highlighted the extraordinary ability of some organic materials and living organisms to survive the harshest imaginable environments.
My geology professor also highlighted thee issue in 1971 with his researh into how coal and petroleum were being formed in geological strata. Sampling of new coal beds in Florida’s everglades were turning up some amazing examples of biological organisms survivng the process for extraordinarily long timeframes.