I personally wouldn't get concerned about that.The front of the house where the lights will be installed faces south and without a huge amount of work and cabling, the photocell will also need to face south. I'd assumed that facing south was probably the best scenario however reading the instructions for the simpler NEMA photocell, I find the instructions state it should be positioned facing north or alternatively as close to north as possible, to avoid damaging the photocell. I can't see any reference to such an instruction in any of the more complex units.
One would obviously expect that (all other things being equal) a south-facing photocell would 'switch on' a little later in the evening and switch off' a little earlier in the morning than would be the case with a north facing one.
Beyond that, they really should not be selling an outdoor photocell which is not designed and constructed so as to be able to stand up to a south-facing environment for a good few years. For what it's worth, I have a couple (of 'basic' ones) here, one facing ~SE and the other ~SW and, in around 35 years, I think that one has been replaced once and the other twice - which I don't reckon is bad going.
Kind Regards, John