It looks like Serial RF Pro is using HopeRF HM-TRP-433, and the specifications sheet for that module says it has a minimum 414 MHz, typical 434 MHz, and max 454 MHz.
The other frequency bands (470/868/915 MHz) apply only to those other HopeRF modules (HM-TRP-470, HM-TRP-868, HM-TRP-915) which are not used by Serial RF Pro, so it is wrong to mention them in any of the Seeedstudio details. You should only describe 414 MHz to 454 MHz as its range.
Alternatively, would it be possible to get a version of Serial RF Pro based on HM-TRP-915? I am very interested in a project that requires that frequency range. I’ve created a “wish” for it here: seeedstudio.com/wish/?p=1444