I think the (very) simple answer is 'yes'.
The more complicated answer is that it depended upon the quality and design of the item. For example, the early unlimited weight designs PP1, PP2, PP3 had fire polished bases (like Strathearn) until 1978. Afterwards they were hollow ground and polished. Early PP4 and PP5 weights had a flat polished, star cut base, changing to hollow ground and polished in 1972. Many unlimited designs only ever had hollow ground, polished bases.
I think all the Limited Edition Annual Collection paperweights had polished bases.
The Perthshire Paperweights book by Mahoney and McClanahan (on my website book list) gives comprehensive details of all these changes.