That would depend on how you interpret "synthetic based"

(but I'd tend to agree with you).
As usual with FIAT, the recommended oil is a Selenia one (WR) and these are normally (at least for the newer engines) prohibitively expensive in the UK.
It is surprisingly as cheap as chips here, though:
https://www.shop4parts.co.uk/?name=store&op=Product&ProdID=2898
...and buying a 5 + 2 litre (just to be safe), would take you over the free delivery price, I think.
(I must admit, I was surprised by the price, it isn't widely available, but might be a bit cheaper elsewhere).