Further searching revealed this:
"Among the apostles - This does not mean that they “were” apostles, as has been sometimes supposed. For,
(1) There is no account of their having been appointed as such.
(2) the expression is not one which would have been used if they “had” been. It would have been “who were distinguished apostles;” compare Romans 1:1; 1 Corinthians 1:1; 2 Corinthians 1:1; Philemon 1:1.
(3) it by no means implies that they were apostles All that the expression fairly implies is, that they were known to the other apostles; that they were regarded by them as worthy of their affection and confidence; that they had been known by them, as Paul immediately adds, before “he” was himself converted. They had been converted “before” he was, and were distinguished in Jerusalem among the early Christians, and honored with the friendship of the other apostles.
(4) the design of the office of “apostles” was to bear “witness” to the life, death, resurrection, doctrines, and miracles of Christ; compare Acts 1:21, Acts 1:26; Acts 22:15. As there is no evidence that they had been “witnesses” of these things; or appointed to it, it is improbable that they were set apart to the apostolic office.
(5) the word “apostles” is used sometimes to designate “messengers” of churches; or those who were “sent” from one church to another on some important business, and “if” this expression meant that they “were” apostles, it could only be in some such sense as having obtained deserved credit and eminence in that business; see Philemon 2:25; 2 Corinthians 8:23."
https://www.studylight.org/commentary/romans/16-7.html