Basically a simplified variant of the methodology the strategy could take is you can build a distribution of OSRS gold
the amount of sell offers that get filled of a specific thing in a particular time interval. In the event the sudden way more sell offers are becoming filled for apparently no reason, you know that item is a sink thing. Then you are having no impact if you do not fill the market offers. As another user suggested maybe the best way to fight this issue is simply buy the things all at once (after the fact) but I believe that might raise other potential issues such as developing a weird risky marketplace based around sudden price spikes, where folks invest in crashed items only for an opportunity their thing will get picked. The item crashes 9, then if it does not. I guess, if that an issue people care about or if its worse than the scenario is another argument.
If they wanted to utilize runelite/osbuddy data they'd be idiot. To get a general price it works and you can see when items that are normal are rising/falling. But, there's been a **** ton of scammers and cost manipulators for OSbuddy and runelite suggested cost trackers on reduced trade volume items and even retailers efforts to manipulate popular products. It's been a massive problem a random occasions, so sure, if you want to move all in on an item which quite likely could just be a random scammer jumping/dropping the osbuddy/runelite price then proceed, because those customers track any completed offers, it could literally be the same person at purchase limit for a product selling them 100 times over and over and it messes up osbuddy and runelite records but not the Jagex ones.
Also the idea that there'd be some difficulty in the speculative market for an item buyout at the end, which I suggested in the first sentence of my opinion once I said you're assuming they buy them as the gp comes in which doesn't have to be the case, does not make any sense. There is literally thousands of items. It is not like we've got a list of 10-15 potential things to be seeing, there's easily over 100 to all be watching and using a program doesn't help when when it may be a manual choice by jagex to select something in the end of the day, you don't need to get it automated, that's just asking for issues to happen. They could also have things in place to flag some things from their prospective list that are being stockpiled too far as not to do this item.
Another easy solution would be to simply have buyouts throughout the day from a list of things rather than have a single thing. Say each 100m dropped, they'll buyout an item and then the next 100m goes towards a different thing or if 100m isn't reached, force it at a particular time period to use whatever it's. All of your assumptions are that jagex must use the most simple way of implementing this idea or will. There's literally an unlimited method to complicate it with small tiny tweaks which make it almost impossible to buy RuneScape gold
forecast or abuse, especially if any step has any kind of human involvement it throws computer learning the door almost entirely.