2. Question: Why can’t the view that holds we eat milk products on Shavuos because the Jews didn’t have checked sharp knives right after the Torah was given to properly slaughter animals, hold that Hashem gave us the Torah on Shabbos?
A. The medrish Pirkei diRebbe Eliezer (46) holds the Torah was given on Shabbos the gemara in Shabbos 86b holds it was given on erev Shabbos.
B. A knife has to be checked for no nicks to be sure there is a smoothe cut by the shechita. As soon as Hashem gave the Torah and obligated us in all the mitzvos at matan Torah which is Shavuos they didn’t have any kosher knives to use that day to slaughter animals, so in commemoration we have a custom to eat milchig on Shavuos.
Answer: If Hashem gave us the Torah on shabbos we couldn’t anyways slaughter because of shabbos so there would be nothing special to commemorate. (See Dirshu Mishna Berura 494 footnote 18)