The metrics used in this paper are... deeply flawed, to the point that the authors admit that they label nearly half of known good papers in a curated sample as "fake" -- and particularly likely to generate false positives for researchers whose institutions don't, say, run their own email systems (as is common in large chunks of the world). Here's a rundown of the flaws from an epidemiologist with a sideline in scientific communication:
https://fediscience.org/@ct_bergstrom/110357259338364341