I think that article shows a certain kind of Mahāyāna apologetics in a 'muddy the waters' kind of way, which goes something like: "Well all the canons are equally unreliable so we might as well pick one at random"
. Yes, we now know what the Pāli canon has been edited too, and most of the Abdhidhamma probably wasn't spoken by the Buddha or Sāriputta Thera. Which is a far cary from the Prajñāpāramitā Hṛdaya (which I think is a beautiful piece of writing, btw) being written in China. The provenance of the Nikāya/Āgama literature is, in general still quite good compared to much of the Mahāyāna literature.
This post by Ven. Sujāto, and the subsequent comments have some good points: Is the Lotus Sutra authentic?
"Delighting in existence, O monks, are gods and men; they are attached to existence, they revel in existence. When the Dhamma for the cessation of existence is being preached to them, their minds do not leap towards it, do not get pleased with it, do not get settled in it, do not find confidence in it. That is how, monks, some lag behind."
- It. p 43