I think we can give frosty base finishes a bad rep sometimes. I have had a few good AVeM pieces that had bases that was polished to frost. Most of my Murano pieces have been completely polished, but there were the exceptions. I wondered if the companies may have been making a large number of pieces, so had to skip the final polishing -- it does take a lot of time. If the base is nice -- and yours looks nice -- having a slightly frosted base doesn't rule out Murano.
While we're on the subject of bases -- many of the best American art glass studios do not polish the base of vessels at all. They ground and leave it au naturale, hopefully with a signature.