Something something modern gear caps at 25%, old pre-i119 gear doesn't.
And everyone errs on side of caution something something.
All gear caps at 25%, or rather 256/1024.
Most gear also lies to you about the value. It is impossible to have an exact integer value that is 5% of 1024 as 1024 * 0.05 is 51.2. Whichever dev made that gear needs to type in 50, 51 or 52 into the value for that gears haste, all while putting "5%" in the string description field. If the dev put 50 into the effect field, then it will be 50/1024, 4.88% haste. If they put in 51 then it'll be 4.98, and 52 comes out to 5.07. All the older developers just did the route and put in "50" for 5%, or "30" for 3% and so forth, resulting in "25%" really being 24.4% (250/1024), which is under cap. Going "26%" meant 260/1024 and was over cap, which is preferable to under. Recent developers seem to put a more accurate value like 52 instead of 50, 103 instead of 100, making the description field more accurate.
I've explained it previously, for "reasons", FFXI server code doesn't do fixed point percentages, instead preferring to add / delete binary decimal places to create the effect while using just integers. It causes all percentage values to act in slightly off ways that what regular decimal math would predict.
