Hello. So, my friend just sent me a message about something they’ve seen. There was someone who was stealing people’s DeviantArt usernames to sign up on other sites, and 5 months ago, they posted these drawings on an account that was named after someone on DeviantArt who had a very similar style:

This person made a post on their main account 26 days ago where they showed some new art. This is what that art looked like:

Another recent piece of art they posted from less than 5 months ago:

More new art from them:

When my friend confronted them for this, they responded with “I changed mediums” to explain why the more recent art looks so different from 5 months ago and asked my friend to “find the original if you think it’s stolen”, but before they said that, they had lied about not deliberately taking people’s usernames. The real person’s account didn’t have those exact three topmost drawings, but did have a very similar style and level of professionalism to the art.

I am not an artist, so it’d be preferable if any artists could chime in on this and whether a change of mediums would explain the differences or if this is bonafide art theft.

TL;DR the person who uploaded the first 3 drawings is saying them changing mediums is why their new art doesn’t look as good. Is this plausible?