When you add a thousandth of an inch clearance between the blade tang and the pivot pin (just so the blade will move you know) and another thousandth between the lock bar and its pivot and multiply that by the length of the blade, sometimes it comes up to enough movement at the tip to detect. If it bothers you, don't buy folding knives, stick with full tang fixed blades. This is not addressed to you specifically of course, it is general advice for those who commonly whine about "lock rock" and other similar "issues".
Of course not all folding knives have "lock rock", or similar "issues", which I'd hope you're aware of.
Some Spydercos definitely do have it, some more than others. Even some of the newer ones.
As to "general advise", as you wrote,
Nothing wrong with just calling it like it is. Yes, some Spydercos do have "lock rock". I've noticed it on some of my back-lock knives. In fact, I'm carrying a 1st Gen PacSalt (pinned, square handle, square clip with big screw, big jimping), and it definitely has a little "lock rock." Some of my back locks have more than others, and some none that I can tell.
A buyer doesn't need to, as you wrote, "don't buy folding knives" though, sheesh...
Do make informed decisions, before spending your $$. Do some searching via the internet for things like the model you are interested in, and "lock issues" or "lock rock", etc... If you can somehow put one in hand before you spend your money, do. If you call them, some of the internet sellers will check the knives for it, or whatever you ask, before you spend your money.
A bit of effort can go a long way toward being, or having, a happy, satisfied customer. Those are the ones you'll likely see again, and again - will refer others, etc...
The money spending customer who spends their hard earned money shouldn't have/get any undesired "surprises" when they get the knife they paid for, without ever being able to actually see and/or hold it before hand...
I get that it may not be an "issue" for a lot of folks, but it is clearly an "issue" for some folks too... And while it may not be an "issue" for some, that doesn't in any way mean that, as you wrote " those who commonly whine about "lock rock" and other similar "issues"" are whiners, sheesh again...