And having an open tripod is no more pre-staging your equipment than having your bipod down.
It's not in position on the stage any more than the bag on top of the barricade used in your analogy. It's in the exact same position all your other gear is per the usual stage description, "all gear in hand".
The explanation given for the tripods in an undeployed position at the start of a stage was to simulate a real-world scenario.
Nobody carries their tripod around with the legs extended and locked out into position. Regardless of if you're hunting or if you're in a combat environment, you just don't do it. On the other hand, there are people who do carry their rifles with the bipod legs already set in position. It doesn't interfere with a rifle sling, and since I personally don't have a sling I find it substantially easier to pack my rifle with the legs extended on my Atlas bipod than them flush with the rifle (the legs rest on my shoulder, the butt stock in my hand).
Bipod deployment also takes less than 5 seconds to complete, while tripod deployment will take substantially longer. The MD could easily say that you have to deploy your bipod on the clock, but that doesn't fundamentally affect the match in any way because bipods are a 5 second or less deployment. They only specified tripods because only tripods make a fundamental difference in how the stage will play out, the bipod deployment literally doesn't matter at all because it's so quick.
Understand, by newer shooter I dont mean the guys at their first match. I mean the guys who have been at it a year or two, maybe even longer, and are still improving. That's 70% of the field of any given match.
By that definition you're including some of the top shooters even as "newer shooters", because not all of the top shooters have even been competing in PRS for more than a year or two and everybody in the series is still improving. It means nothing with that definition really, because it's broad enough to include shooters of all skill levels.
The large majority of them aren't spending $1000 on tripods. They are buying Leofoto and other decent less expensive options. Or they are buying aluminum off Ebay or used carbon. But make no mistake, nearly every shooter in the squad either owns a bipod or can borrow one.
A Leofoto tripod will run you $650. A good ball head will cost you $200. A good dovetail clamp will be an extra $75. Add in any extras like tripod feet or a hog saddle (if you don't have a dovetail rail on your rifle) and you're still easily over $1,000 for the tripod setup. In two years of shooting matches, including several national matches, I have only seen 4 aluminum tripods brought to PRS matches in total while having similarly seen dozens and dozens of carbon fiber tripods.
As far as borrowing tripods go, that's certainly possible but the people who borrow a tripod at the match aren't the same people who rely on tripods for their stage strategy. They remain unaffected by this rule because they're already used to practicing with no tripod. The only people affected are those who rely on a tripod to effectively engage their targets.
It should be noted I have nothing against the use of tripods, but I do agree with the assessment of many that it's a bit of a "gamer device" to add stability without having to practice. I also believe it's entirely reasonable for a match director to design stages with a reasonable scenario in mind, and no reasonable scenario includes someone carrying around a fully extended and deployed tripod instead of a collapsed and folded one. Shooters should be tested in their ability to shoot both with and without tripods, because it's a useful skill but not one that should be used as a crutch.
I'll just leave you with the following question, since you believe tripod deployment on the clock provides some shooters with an unfair disadvantage:
Do you similarly believe that stages requiring the use of a tripod (such as at matches sponsored by RRS, where one stage requires you to use their stage tripod) provides some shooters with an unfair disadvantage? It would be logically consistent for you to believe this, since not all shooters have the opportunity to practice regularly with a tripod in the same way that tripod shooters might not practice regularly at either deploying quickly or not using their tripods.