As I understand it, things like these rails are straightened by stretching. They come from the extruder fairly straight and get stretched to the final tolerance. I would assume that this tolerance varies to some degree by the different manufacturers. I would also guess that there is a lot of complex calculation going on with that. As things are stretched, they get thinner, that would have to be figured in, for the rail to turn out as required. From what I have heard, the guaranteed straight part of a Festool rail is the edge of the raised section that is nearest the splinter guard side, not necessarily the whole thing, there may also me some machining going on too. I have no idea where Makita considers the straight part to be or exactly how straight they call acceptable.
That said, it may be within spec in the first place, whether that's good enough or not.
Also, it may be able to be perfected, but quite costly to do that. Trying to straighten it yourself might make it worse.
Some people I have worked with over the years call this the 95-100 rule/thing. When something is at 95%, trying to make it too 100% usually makes it worse. Then either it costs so much in time or money to get back to where it was before, it's not worth it.
That said, under 1/16" bow in almost 10 feet is not horrible, unless you want to match two edges together on long panels, where the error would double. If that is the case, it might be better to do a mirror cut, where both panels are cut at the same time, parallel to each other. Then even if they are not perfectly straight, they are the same. A router and a straight edge make it easy, just the tiniest amount needs to be removed.
