Yup, that. ^^
I've even seen max loads in one book be about what the STARTING loads in another book are.
Work up slowly until you find the load for your rifle. Published data is a GUIDELINE.
I've had high pressure signs on several loads WELL under the max load, my rifle / components must behave differently than their test barrels.
I've also been able to push several rifle loads well BEYOND the max load without any high pressure signs (either on casing or velocity).
I've also had a load behave perfectly normal in one rifle, only to show EXCESSIVE pressure signs in another. (This is how I found out that different twist speeds play a role; a pair of AR-15's with different twist speeds but otherwise the same, on gas tube length / barrel length behaved WAY different with some 62gr bullets I loaded. One was fine, the other was flattening/cratering primers.)
The number of grooves, lands placement, twist rates, bend in the barrel (a lot of barrels are bent somewhere, very few are
perfectly straight), different harmonics, heat warpage (some barrels get tighter when they get warm, some looser, depends on steel stress), and many other factors play in to internal ballistics.
So does temperature (on some powders). Different lots of powder / primers. Etc.. etc.
The short of it is, there's so many factors at play, ultimately YOU have to work up a load that fits your rifle/needs.
Which means the reloading manuals are guidelines.