It doesn't convert the NRO to an NSP, all you're doing is creating an NSP file that is basically a "Shortcut" that redirects to the OFFICIAL RetroArch NRO file. People keep confusing this with the NSP file that RetroArch came with once upon a time. THEY ARE NOT THE SAME THING! The original RetroArch NSP wasn't a "Shortcut" like when using Nro2Nsp, but instead it basically contained what is now in the NRO file.
He already responded to this question in the
dynarec thread and the only reason given was "it's not future proof in any way". So I guess as long as you realize that using NSP forwarding might not work in the future then apparently there is no other reason to worry about it.
Like I said in the quote above, I think most people are confusing using the original RetroArch NSP as being the same as using Nro2Nsp, which are clearly two different things. With Nro2Nsp you're basically creating a "Shortcut" that simply redirects to the official "retroarch_switch.nro" file. Whereas the OFFICIAL RetroArch NSP that was available from RetroArch was NOT a "shortcut" that pointed to the NRO file, but instead it basically contained what is now in "retroarch_switch.nro". There was never an NRO file that
Just take a look at the file sizes...
Original "Official" RetroArch NSP: 11 MB
Current "Official" RetroArch NRO: 10 MB
NSP file generated with Nro2Nsp: 609
KB
CLEARLY you can see that NSP files generated using Nro2Nsp do not contain the same data that the offical RA NSP did. That's because they are simply "Shortcuts" that point to the OFFICIAL "retroarch_switch.nro" file.
I have yet to experience ANY issues using these Nro2Nsp generated NSP's, and until someone comes forward and shows PROOF that using these Nro2Nsp are the devil, then I'm sticking with the more convenient solution.