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It's a good question, and there are arguments on both sides.
By R16 Cinema was already a hugely powerful and refined program, and a lot of great work has been produced in it. It remains everything you need to learn the main areas of Cinema - particularly modelling, materials, Xpresso, rendering and more specialist things like Hair, bullet dynamics, cloth and sculpting. Although a lot of these things have been rewritten or adapted for the new core now they are haven't changed a great deal in functionality so R16 would still be fine to learn these things in. R16 was also in what I would call MAXON's 'Golden Era' of maximum stability and reliability, so if you have the latest update version of that it remains a solid option.
The modelling tools (knife related ones especially) have been quite a bit different and better since R18, but they remain similar enough that if you learn the way they used to work, it won't be a massive disadvantage when you get the newer ones.
But on the corollary, things didn't stop getting better since R16 either. There is a now a brand new core, which means everything, including the viewport, is more future proof, powerful and efficient, MoGraph and deformers got a serious upgrade with R20 in the form of Fields and in modelling the volume builder,and overhauled Voronoi Fracture and you won't find anyone who has used these asking to go back to the way things used to be done ! Most recently MAXON sorted out UV mapping, which is now a good deal easier and less annoying than it was prior to S22.
So, if you are serious about this software then it follows you want access to the most powerful it can be, and the most flexibility it can offer you, then I would say yes, that tips the balance in favour of upgrading to R23 straight away. But if you are short on cash, or it would be a struggle to afford it right now, then there is no harm to your learnings if you did 6 months with R16 first.
CBR