why a high end phono preamp?

Op, I hope you don't mind if I ask perhaps a related question here.  Are all stand along phono preamps both MC and MM?  If a person knew they were only going to be using MM can a MM preamp only be purchased, perhaps even at a price that reflects it not having the not necessary MC electronics?

Yes you can purchase just a MM phono preamp Soundsmith for one makes them, I'm sure that there are also many others available.

Are all stand along phono preamps both MC and MM? If a person knew they were only going to be using MM can a MM preamp only be purchased, perhaps even at a price that reflects it not having the not necessary MC electronics?

Most inexpensive phono sections are MM only. You need more gain and a good noise floor for LOMC cartridges- and that costs more.
One other thing about a good phono stage. A good one will exhibit less ticks and pops due to better RFI resistance and good overload margins.

Are all stand alone phono preamps both MC and MM?

There is a school of thought that designing a lower gain MM only phono stage is optimal and using transformers to deal with the additional gain of an MC cartridge. Given the diversity in characteristics of MCs (both output and loading needs) manufacturers often elect to leave the selection of transformer up to the user.  Allied to this is a belief in keeping the phono stage as simple and option free as possible to focus on the purity of the amplification and equalization

That's at least the philosophy of the maker of my phono stage, which is a pretty high end model and I will say that for this end user at least it works well

OP, your suggested Clearaudio Nano V2 phono section looks good and proportionate to your other gear in terms of quality and expense. What are you contemplating for a phono cartridge and speakers?