A more satisfying explanation is given for the migration of the pericope adulterae to a place after Luke 21:38 in family-13 manuscripts (et al). As Chris Keith has already shown, the insertion of the pericope adulterae to follow Luke 21:38 is an effect of treating the passage like a lection; the movement to this location made the lector’s job easier; the lector could thus find the lection for Oct. 8 (the Feast of Pelagia) near the lection for Oct. 7 (the Feast of Sergius and Bacchus). Everything you have read or heard to the effect that the pericope adulterae is shown to be a “floating anecdote” by its appearance after Luke 21:38 in family-13 manuscripts can be safely ignored.
A few shortcomings of To Cast the First Stone may be covered briefly:
To Cast the First Stone: The Transmission of a Gospel Story is Copyright © 2019 by Princeton University Press.
P.S. I have written a book, A Fresh Analysis of John 7:53-8:11, maintaining that the pericope adulterae was originally part of the Gospel of John. It is available as an e-book on Amazon.