Here Oliver Cowdery initially wrote things, but then he crossed out things and wrote inline the correct sayings, undoubtedly the reading of the original manuscript (no longer extant here). The normal reading in the Book of Mormon text is “to make an end of one’s sayings”:
There is also one case of “to make an end of one’s saying” (that is, where saying is in the singular):
For discussion of the possibility that this singular saying could be an error for sayings, see under 3 Nephi 5:19.
In the Book of Mormon text, there is only one actual example of “to make an end of things”, and in that case Oliver Cowdery initially wrote sayings in 𝓟, then virtually immediately corrected it to things:
(See under Mosiah 6:3 for discussion of why things might be more appropriate than sayings for that passage.) Oliver’s initial error of things in Mosiah 13:25 might have been influenced by the earlier occurrence of “made an end of all these things” in Mosiah 6:3.
Summary: Accept in Mosiah 13:25 the corrected reading in 𝓟: “after Abinadi had made an end of these sayings”; here we can be confident that Oliver Cowdery corrected the text to agree with 𝓞, given that the word sayings was written inline in 𝓟.