The Gemoro brings a Machlokes of Avos Haolom.
The Gemoro asks:
“Who were the Avos Haolom?” and answers “ it was R. Akivah & R. Yishmael.”
The Korban Haeidah explains Avos Haolom = Tanaim Harishonim. (early Tanaim)
When the Rambam quotes Chazal, he usually writes Omru Chazal or Omru Chachamim. There are a number of times where he writes
Omru Chachamim Harishonim (last week)
The Rambam (Hl. Shabbos 30 : 7 ) writes Omru Chachamim Harishonim
עשה שבתך חול ואל תצטרך לבריות .
This Mamar is from Reb Akivah
It is very likely , when the Rambam quotes Ma’amorim from early Tanaim ,
He refers to them as Chachamim Harishonim.