Almost certainly they're only in the Java 7u10 (x86 for x64) package because they are only required in that scenario (dealing with the JRE7u10 x86 installation on an x64 system).
Yes, the 7u10 installer should automatically handle the uninstallation of earlier versions of JRE7. The fact that the packaging team found it necessary to include an explicit instruction to uninstall JRE7u7 suggests to me that something in JRE7u10 is broken. No great surprise there, as we've recently been entertained by numerous defects in JRE7, another one discovered just as you were writing this post, and JRE7u11 was released by Oracle yesterday. (No doubt we'll be working on packaging it today.)
All of the Java packages have commands to check for open files and terminate processes. This has been a basic component of Java packages since the first one included with Patch Manager - in fact, this capability, for JRE updates, was one of the primary reasons PackageBoot was created. I'll take a look at the packages and see if there's anything notably worthy of comment; if so, I'll write a blog post and/or have a KB article written.