The gemarra states that Moshe did three things of his own accord, and Hashem concurred (Shabbos 87a; Yevamos 62a; Shemos Rabbah 46:3 (slightly different list); Avos D'Rabbi Nosson 2:3 (lists four, the three from the gemarra and the extra one from Shemos Rabbah)).
Chazal also tell us that Hashem told Moshe to warn Pharaoh that the firstborn will die "bachatzos halailah", at the stroke of midnight1. Instead, Moshe said "kachatzos halailah", approximately at midnight (Brachos 4a).
The above list doesn't include this occurrence. Do any commentaries note that this is another case that was left out, or explain why? Or do any say that Hashem in fact did not concur with this change, and why?
1 This is the simple understanding of the gemarra, starting from Berachos 3b, the understanding of Tosafos (Berachos 3b), Maharsha (ad loc.), Rabbeinu Bachaye, Mizrachi (according to the Levush), Maskil L'Dovid, Tzeidah LaDerech, and Ba'er Heitev. Cf. Levush and Be'er BaSadeh, who are appalled at the suggestion that Moshe changed what Hashem said, and assert Hashem told Moshe to say kachatzos.