It's the opposite on my box. I think it's because of the HT. When we have HT and keep the setting on Stereo, the volume is much louder. But on TV, it looks to be opposite. May be, if there is a Dolby option on TV it works the same way as on HT. If not, it behaves a bit different.
As for the volume control, you can just keep the STB volume on high (Assuming you kept the setting on Stereo) and pair the Volume buttons with the TV remote so that you don't need to keep the TV remote.