I agree completely, however the main LFO does have a much wider range than the vibrato one, so for some types of synth-style vibrato it is actually the only choice. But the dedicated vibrato LFO not working across layers is frustrating and I cannot imagine why Nord thought the current situation was logical, surely they have tested a patch with more than one layer that has vibrato on it...
For me personally, because I am pairing this with a Prophet X, I have my deeper bases covered. However if someone only wanted to use one synth this has some strange limitations for sure... As part of my setup I am happy with it now that I found the right keyboard to pair it with but if it was my only synth I would still be very disappointed.