it can mean it will let interference in at a higher range by outside electrical sources.
cable frequencies are between 5 and say 900 in the scan range hence 5-1000mhz is what vm use.
to your point above - are you saying you should get a splitter as close to the vm range as possible i.e. 5-1000mhz or would a 5-25000 MHz splitter work fine since it covers the whole range? I have just setup my first cable box for a mate and his hd channels are buffer city so I'm going through potential fixes.