it can 'runoff' anywhere, so yeah...
if no water is coming out bottom, you've never saturated the cooc properly. if you have dry spots inside, it'll become a bit hydrophobic and repel water if bone-dry in a patch... no problem, just water a bit more.
great thing about coco is it's basically impossible to over-water (unless extremely compacted and all pith or fine particles). Don't be afraid... get that 20% runoff or whatver you like. if oyu see it coming out sides of pot, it might be what i described above.. get that area a bit more until it looks like water is traveling down again.
don't flood it.. don't disrupt roots... use a real watering can or something with long spout like a watering can... a watering wand and tank is a priceless tool to have (~$15). makes it easy and can reach to corners.. doesn't funk up top soil or disrupt roots when applying water.