Of course, I will agree with you - this is language about the Feast of Weeks. The first Sabbath in the Week of Sabbaths... Thanks for a concise explanation.
Yup! That's why it's called the "Feast of Weeks". 49 days with each individual weekly Sabbath enumerated as well as the other week days by counting the Omer.
And that's why the Greek says (in all four gospels)....the first of the Sabbaths.