I think that holds for the likes of Billy Meredith, post-50s there's very decent footage, just rarely online. It would be fair to say most people engaged in doing stats for a videogame haven't seen these guys live and that where there's little footage online the most likely knowledgeable sources would be locals, which can introduce a bias. That's why I overlooked the early Joya stats, they are so much better they are most likely the work of an overexcited River Plate fan, but the ones I quoted makes sense to me relative to Jairzinho.
They are consistent with what I've seen and heard, not just from Peñarol fans but documentaries involving the likes of Pelé and Santos authorities. For Santos' President to say someone was unplayable and impossible to disposses, when Pelé played for them... that's no small praise. Pelé had a show in Brazil a few years back and one of his first invitees was Spencer, who he said was one of the best players he had seen and had gone toe to toe with him for years with the advantage of being a better header of the ball. I remember him putting forward himself, Spencer and Eusebio as the most formidable forwards of those days and, when mentioning him still being the top scorer of the Libertadores Cup ("that's one record Pelé doesn't have", cheeky git), had a slight dig at Spencer saying no one else had Joya servicing them. While Spencer could have replied that he instead had Garrincha, Jairzinho, Rivelino, Tostao, Gerson... all he did was acknowledge how much he had enjoyed playing with Joya all those years. They were like two peas in a pod, a brilliant twin threat for any defence, and you couldn't contemplate one without the other. I think I mentioned before how they died in the space of four months and a song dedicated to them two topped the charts here, forty (40!) years after their peak.
Seriously, how hard is it to imagine that he would be comparable to Jairzinho when he was an integral part of a strikeforce that reached five out of the first seven Libertadores finals? And had their been an away goals rule they would have won all five, not just three. But no, let's ignore all that and focus on World Cups as the goal standard, a massive disservice to a player from Peru who chose not to play for Uruguay hoping to get his country into the WC some day (despite there being a policy of not calling up those playing abroad). Let's also assess George Best on his World Cup form while we are at it, shall we?