Definitely can confirm this bug. Happens every time when I'm viewing someone else's profile and then use the dropdown in the top right to select my own profile page. It'll show my header image and banner, but all the content below it will be that of the previous profile I was viewing. Hitting F5 fixes it.

Allowing shouts to be visible on a person's page keeps the experience open. Private messages are private; shouts are meant to be like a semi-open social space where a person can say something directly to someone and others get to see who keeps in touch with them. A few of the artists I follow were only discovered by me after seeing them leave a shout on another artist's page, after which I clicked their profile and looked them up.

Shouts are also meant to be informal, and people who are less comfortable initiating direct conversation in private use this space to engage with someone without really feeling like they have to maintain the convo. Sometimes comments on a shout page get taken into private message space just because I thought that person was cool and I felt like actually having a 1-on-1 with them.