On the betawiki page, is stated that only the "Premium" edition had been made available.
https://betawiki.net/wiki/Microsoft_Off ... build_2221
While looking for other things, found these:
https://archive.org/details/ms-bep-vol42
https://archive.org/details/ms-bep-vol43
These are disk sets from the Microsoft Beta program. Each volume consisted of serveral, widely differing betas.
Volume 42 includes Premium edition.
Volume 43 includes Professional edition.
Even though the install.msi in both builds state "9.00.2221", the ISOs are authored with different tools, and have different dates.
Volume 42 - Disk 1 was produced with Buzzsaw (very common with O2K builds), and Disk 2 with CDIMAGE 2.32
Volume 43 - Disk 1 and Disk 2 was produced with CDIMAGE 2.27.
And there are numerous other differences in structure.