Saudis will definitely accept payment only in Saudi riyal.
You do know the Saudi riyal is pegged to the USD at a fixed rate of 3.75 SR to 1 USD, right?
So, using the royal or the dollar is the same, that's why nobody really cares about that, in order to keep the peg they need reserves in $, getting paid in shitty fiat currency that can't be exchanged is a no, and even if they do accept yuans they will use that again for conversions!
and you think them using the riyal will still have USD demand?
You don't understand what a peg is, right?
For somebody to keep a currency at a peg you need t have the reserve in the said currency available, so if I sell you 100 riyals you know for sure I have $30 backing their value, otherwise you would not accept my currency and chose some other shitcoin like the Russian ruble, the Iranian rial, the rupee...you know all too jokes BRICS currencies.
Second thing, which again proves you don't know how settlements work..
If a barrel of oil is $100 and Saudi Arabia sells it for 350 riyals, it still sells them to the same USD value, if they drop the price to 300 they drop the price in USD also, their coin not being independent it means everything will still be priced in $.
Want proof of this? good!
What's the price of Bitcoin in riyals? I can already see your pikachu face since you're obviously going to use the $ to come up with that!
And this is the reason nobody cared about it!