Yes I understand golf.
Here is another article you won’t read that says you’re wrong. If you did read it, I’d advise you pay particular attention to the statements of the former PGA pro who occasionally one-off caddies on the LPGA.
http://www.realclearlife.com/sports/was-matt-kuchars-5k-caddie-payout-after-winning-1-3m-actually-wrong/
Of course I will read it - I'm a huge golf fan. I play and watch (when I can), I listen to golf podcasts on my way to/from work, and I read a bunch of articles on all sorts of golf-related topics.
I will admit that 'realclearlife' is not a website I visit for golf-related info, and this article is the first one I've seen that suggests that this is somehow standard for fill-in caddies. Have you actually listened to the podcast they are quoting? It's nowhere near as definitive as the article suggests, and even Hawley says that there is discretion for fill-in caddies (he just thinks $5k is too low). His opinion is largely based on the fact that Kuchar won a large amount and paid the caddie a small amount, when he had the opportunity to do something life-changing.
And if you've just gone searching for stuff that supports your view that 10% is the accepted standard for fill-in caddies, you've probably ignored the overwhelming number of people - including Ortiz himself - saying that he doesn't think he deserves the 10% that a regular caddie would get paid.
Here's a few examples:
https://golfweek.com/2019/02/17/golf-19th-hole-what-a-caddie-work-worth-matt-kuchar-debacle-leaves-us-plenty-to-ponder/"Not many guys on Tour are eager to talk about the issue since Kuchar issued a statement saying that he will finally pay Ortiz what he asked for (which was $50,000). Ask around and you won’t find many who believe Ortiz deserved the standard 10 percent a professional Tour caddie would expect, but even fewer who think five grand was acceptable."
https://www.golf.com/news/2019/02/12/they-can-keep-their-money-kuchars-fill-in-caddie-breaks-silence-over-pay-dispute/"
Ortiz said he did not expect to be paid what a Tour caddie would have made, but said he believed his work and contribution toward the win was worth $50,000."
https://www.businessinsider.com.au/matt-kuchar-caddie-cheap-tip-el-tucan-2019-2?r=US&IR=TPer Michael Collins (former PGA caddie): "A couple of players told me if right after the tournament he writes the guy a check for $US35,000 – which is still less than 5% of a commission – he would have been seen as a hero,” Collins said. “Now most of the caddies and players that I talked to have said $US50,000 is the number, and one player said even if he pays the guy $US50,000, he’s never going to live this down"
Bob Harig, the senior golf writer for ESPN, and one of Kuchar's biggest critics on this issue gave this reply to a question on Twitter asking why he wasn't paying the 10% - "Because nobody believes that is a necessary payment for a fill in caddie. It is understood that is part of a deal for a regular who travels and pays his own expenses, etc"
And finally, if 10% were the 'custom' for fill-in caddies - which it's clearly not - why is everyone now giving Kuchar a pass for paying less than 5%? The reason is pretty clear, even if you refuse to admit it...