I can't explain why someone would say that as it isn't true.
The 1973 preliminary design for the R-73 was a wingless tube with tiny strakes and thrust vectoring. In 1975 Molniya presented two versions, one thust vectoring and the other conventional. Each had advantages and disadvantages.
By 1976 the designs were combined with both thust vectoring and control surfaces and looked pretty similar to the R-73 but with R-60 shaped rear fins. There was a weight penalty but it was deemed worthwhile.
The final design moved to squarer rear fins. All documented pretty well.(e.g. Su-27 Fighter - Beginning of Story by Bedretdinov et al)
Vympel OKB designed the rival K-14 missile without thrust vectoring, but it didn''t proceed past firing trials losing to the R-73.
I don't believe there's an R-73A designation.