In other words, when they said a verse was "updated" (نسخت), they meant that it is no longer to be taken alone to decide a matter, but the "updating" verse must also be considered.
I believe we can substantiate this view with examples that were considered abrogation, and that clearly do not remove the old ruling, but amend
it. A pronounced case is the verse setting "اللعان" rule,
that amended the verse setting the rules for sexual accusations,
On page 114-115 (item 173) in volume 1 of Zaid's book, he discusses how this is considered "partial abrogation" by the Hanafis. The mere use of the expression "partial abrogation," and the obvious fact that the ruling in 24:4 still stands in general, give credence to the assertion that this is a linguistic discrepancy not a theological one.
BTW, I think there is an important benefit for having general rules in some verses amended in later verses rather than in the same verse. This underlines the fact that the rule is not absolute, but subject to exceptions when a compelling situation arises (such as the situation of "اللعان"). If the exception was made in the same verse as part of the original ruling, it is more likely that people would take it as the only exception and that the rule, stated with the exception, is otherwise absolute. In this particular case, another situation might arise that may also be considered an exception, for example rape. If a victim of rape reports the incident, it stands to logic that there is no need for 4 witnesses to prevent the victim from receiving the penalty for slander. It may well be that "اللعان" protocol is applicable in such case. JMHO, and God knows best.