I agree with what they were saying on the podcast, that it is often 'the mark of an amateur'. Someone draws a flower for 20 minutes, then writes copyright info all over it or even a huge signature and date. Instead of a nice flower, I see their ideas of grandeur and paranoia.
Fundamentally I agree with you (see my earlier response).
The trouble is that what you've described above isn't what was described in the podcast. Will referenced a "big copyright "c" in the bottom with their signature"
I want to be fair and not pick on Will here. It's possible that in that brief comment in this one podcast he was picturing what you describe.
But a new illustrator trying to make their way in this industry likely would not.
A new illustrator would hear "pros don't do that".
That new illustrator, looking for clarification, might head over to Will, Jake or Lee's Instagram pages. There they would find multiple posts with no credit line at all!
This is a mistake.
Maybe the guys have a good reason not to include a credit line on work posted online. I've yet to hear it, but I'm always open to a reasonable argument.
My opinion and personal experience is that posting work online with no way to link the work back to the OC is bad advice for an illustrator starting out in this industry at this time.