The Minor Expression has a problem the Expression does not. The birth name is a matter of record: there is a document, and where there is an argument it can be settled by looking. The name a person actually uses has no such anchor, and the system offers no test for choosing between the candidates.
Most adults answer to several names. There is the one on the passport, the one colleagues use, the one family uses, the one that appears on a byline, and the one used in an entirely separate part of life. Different choices among these give different figures, and the difference is not marginal: dropping a middle name, using an initial rather than spelling it, or being Kate rather than Katherine moves the total by enough to change the reduced digit. A practitioner asking the client which name feels most theirs has, in effect, let the client choose the answer before the calculation begins.
The dependence on spelling rather than sound is the same weakness the major name positions carry, and it bites harder here. Transliteration makes it plain. A person whose name is written in a non-Latin script has no letter values until someone romanises it, and competing romanisations give different numbers for the same unchanged name.
Practitioners are generally aware of this and treat the minor positions as the softer, more provisional half of the chart. That is a reasonable way to hold them, and it is worth knowing that the softness comes from the input rather than from the doctrine.