I don't see why the need to buy the same brand rulers/mats. An inch is an inch is an inch.
That being said, you may discover you prefer the markings on a particular brand of rulers over the other ... but that's personal preference, not the need to match the equipment.
As for inaccurate measurements ... I have not noticed that at all.
Perhaps if there are problems it is an off-shore knock-off type? Or perhaps they are metric and not imperial .... a cm is a cm is a cm .... and yes, should not be mixed with imperial inches, etc.!
As for myself, I have an assortment of ruler brands. My preference are the frosted rulers as I get less glare with the lighting, plus the lines are finer for measurement accuracy. The one that has the full grid markings on it is nice, though at times I find it drive me nuts, as it;s not easy to distinguish between 1/2" vs. 3/8" (for example). Again, that's a personal preference ... and I still use that one a lot, as it's just the right size when I am trimming PP work.