True, only if you don't check it :But in the UK this would be pointless, because each MUX in the UK transmits the EPG for all MUXes, with the data for different MUXes being interleaved. So to receive a full EPG you have to receive the EPG from one MUX for one complete rotation of the EPG carousel i.e. keep receiving EPG data until you get back to where you started.
Otherwise, you parallel treatment.
To be sure of it, clear your EPG programs, try only with one tuner, uncheck this checkbox, wait, let's say 10 minutes, yes, you have all channels EPG filled but for how many times ? (minutes, hours ?)
Do the same checked, clear your EPG programs, always with one tuner and wait 10 minutes then ?
You don't have all channels of course, you have only channels in MUX but, for how long ? (minutes, hours ?).
Far for those channels, isn't it ?
And how do you think it is, with more MUX filled in the same time, with the same 10 minutes elapsed ?