Here is the wikipedia definition.
" The Honda I-SHIFT is a 6-speed automated manual transmission (a type of transmission with a hydraulic computer-controlled clutch)"
Basically its a conventional clutch and gearbox with the computer doing the thinking and mechanical servos doing the leg and arm work of changing gear.
If you are absolutely sure the brakes themselves are working properly in every respect it could be a problem with the automated gear changes. Same as a learner driver changing down too early, and maybe releasing the clutch with bit of a jolt. You get extra engine braking adding to the conventional braking making it seem 'grabby' . And being automated it may be unexpected. This is just speculation. I dont know.
As for clutch hydraulic fluid being the cause problem its important not to confuse it with changing the fluid in a CVT gearbox. CVT fluid needs replacing because it significantly degrades,and no longer does its job .
With a conventional hydraulic clutch ,(as used in the I-shift) a different kind of fluid is used . As GBH says the problem here is it absorbs water over time. Fluid is changed periodically as a precaution to minimise the chances of moving parts rusting and clogging. But until any damage happens the fluid itself still functions reasonably well, even with water in it.
Sorry to say just changing the fluid probably wont restore it to working order if parts have already been damaged.Or if there is problem such as a leak, or air bubbles in the fluid that need bleeding out . But do it anyway as a precaution, even if its not actually the cause of your problem. If it does improve it, then thats a bonus.
Its possible there are other adjustmens that can be made, or even expected to be made to I-shift cars and might even be included as part of a periodic service. Or its something else entirely. But these are beyond my knowledge.