Chome360,
I think the answer to your question is yes...
A SIP will continue wicking water into the mix until it becomes saturated, but only if the reservoir is over sized or you keep refilling the reservoir. If you only water with a fixed amount and only when it is needed (dry), the mix will be "properly" watered every time.
Regardless of whether or not you use SIPs to grow your cuttings following this simple procedure may save you from over watering your cuttings. The Reservoir fill amount is only needed in the initial growth stage, once the cutting has fully callused and the roots have "hardened" the SIP can be watered normally.
It seems that several members may have started using the Mini-SIPs without first testing them to see if they distribute the water properly with their preferred mix or whether the wicks and reservoirs are correctly sized. Mini-SIPs are not a panacea, they have to be used within the scope of their design. They will "bottom water" to distribute water evenly in the mix and maintain the mix in an aerated condition. In contrast, top watering washes the smaller mix particles down around the bottom of the cutting, holding moisture and causing rot.
Regardless of SIP designs or planter types and sizes, following the simple procedure linked above will work to keep you from over watering. Simply perform a test on your SIP or Planter and Potting Mix, it will be very easy to see if it will be successful. Find the fill amount and then water the SIP or planter filled with your dry mix, wait an hour or two then dump out the mix in a container to check the water distribution.