No problem exists. If you'll look at the prereqs for xlC.rte again:

> xlC.rte 6.0.0.0 At least 1 of the following must be installed {
> At least 3 of the following must be installed {
> *prereq bos.rte v<5
> *prereq bos.rte v=4 r=3
> *prereq xlC.aix43.rte 6.0.0.0
> }
> At least 2 of the following must be installed {
> *prereq bos.rte v=5 r=0
> *prereq xlC.aix50.rte 6.0.0.0
> }

This means:

EITHER:

(bos.rte before 5.0, bos.rte at 4.3, AND xlC.aix43.rte 6.0)

OR

(bos.rte 5.0 AND xlC.aix50.rte 6.0)

You only need to satisfiy either set; you have bos.rte at least 5.0 and
you also have xlC.aix50.rte at least 6.0.0.0. So you are all good.
Nothing's broken.

How do you figure 'EITHER'? Well, it says 'At least 1 of the following
must be installed', and there are only two (sets of) options.

-Dan