Imagine the following journey:
- Open mobile homepage
- Click Impact module
- Click x edits to other kinds of pages (see all)
- You're on Special:Contributions, had a look over your contribs and now you want to get back to your homepage. At desktop, this is quite easy (click your username in top right). However, on mobile, it's possible that users will try to click at their username on the top of the contribs page (the most prominent username displayed), with something like "I clicked my username to get to homepage, this is my username, so it'll get me back where I was".
I think this can be quite confusing for some of the newbies.