This is yet another example of the difference in the approach to species names between the Cites Checklist issued by the IOS (and updated in the Cactus Lexicon) and the mostly German approach. The IOS, being mostly comprised of professional botanists, tend to focus on the commonalities between plants and so lump together plants into species and have fewer subspecies. The alternate approach focusses more on differences, and so needs more names.
The important thing is to know what a name means, and if it has been combined with another. I tend to favour the IOS approach, but keep in my records (and in my labels) if it is a plant with a different name.
This example of plants which have been lumped into M. albilanata ssp. oaxacana is a classic case in point.