Slow wetting would be something more like overflow incontinence where there's just a light but often trickle of liquid.
Flooding would be a nearly full or full bladder fully releasing such as can happen in urge incontinence. And wetting that wouldn't be considered flooding would be similar but emptying before being full.
For example I'm fecally incontinent, but I do still have control of my urine. However since I wear diapers, it can be difficult to use the toilet for urinating without removing the diaper, and I don't want to do that because then I waste the costly diaper, so I just voluntarily use my diapers for wetting as well. I'll usually do a conscious empty every hour or so, and I've sort of trained my "I really need to go" signal to be very minimal as a result so that just tends to remind me anyways. After an hour, even if I haven't drank much liquid I'll get to the "I don't think I can hold it anymore" stage even though the bladder is far from full. Whereas most people won't reach that stage until they are nearly full.