I tried to find the statement where a selective was not the same as an
incremental absolute but could not find it (thought I saw something like
that).  So it looks like the mechanism is to setup for modified and when you
need a full backup use a selective specifying the entire client file system.

I think you make the most important distinction here between a backup
utility and a storage management product.  TSM is used to manage storage and
its recovery during a failure.  A backup utility is used to perform backups
and hope you can get restores.  That is why I joke about a competitive
product being ???backup, gross no restore (a little play with words).

So, I think we are at the documentation needs to be fixed.