I understand your view.
And yes one can say that it is common among theological commentators (writers online etc) to understand that such penance on Fridays outside of Lent and Good Friday that are not Solemnities or Holy Days- in the USA- is required (giving up meat or a substitution by the person of some other penance).
I readily admit that such is common and such was my long held view too - indeed I even called a very well known Catholic Theologian and argued with him about the matter in my younger days.
And (a different person )- Jimmy Akin the senior apologist at Catholic Answers explains his take -here:
jimmyakin.org/2004/07/since_tomorrow_.html
To which he concludes:
"Thus we conclude that the American bishops have exercised their competence, later acknowledged by canon 1253 of the 1983 Code of Canon Law, to determine more particularly the manner of abstinence by restricting it to a few days a year (Ash Wednesday, the Fridays of Lent, and Good Friday–the last being part of Triduum rather than Lent) and by recommending the continued practice of abstinence on other Fridays. Rome confirmed this document, and thus it is the law for Latin Catholics in the United States.
This also is the understanding indicated in the Canon Law Society of America’s New Commentary on the Code of Canon Law. The commentary on canon 1253 summarizes the obligations and recommendations without indicating that a legal obligation to do penance continues to exist on typical Fridays of the year."
Note that part there too about the Canon Law Society of America’s new Commentary on the Code of Canon Law.
Theologians can differ as I have seen other Canon Lawyers as well on this matter differ on this matter.
Yes there is ambiguity. Hence the disagreement among sound theological minds. I can now see points on both sides (including that such is simply a permitted substitute but that something ought to be done) and I have been on both sides …for me it is solved in practice by simply remembering that it
is a day of penance -so lets do some penance).