Although Shavuos is a biblical holiday, it is never described as “Zman Matan Toraseinu” in the Torah. And there have been some very good suggestions

The first Rashi in our parsha is fairly famous, as his question (quoting the Sifra) of “what connection does Shmita have with Har Sinai?” has

Lag Ba’Omer has come and gone, and we are now in the fifth of the seven weeks of the Omer. With seven days in each