Haha yeah well, all male nipples are still porous, and some male nipples do actually produce liquid... Just saying, mammal nipples are porous regardless of the shape, and when you look up other nipples it is all baby bottle mouthpieces lol also porous
I know what you're saying though, because a nipple could just be like a nub, any thing you are touching that is a flat surface with something sticking out could be a nipple... however with these stems in particular, when you are touching them on the outside, they are dimples you feel, as the "nipple" would be on the inside and never touched... So on top of not being porous, yeah these are just not nipples to me at all!
And so aside from hating the word now, dimples or indents is just a much more accurate description in my own opinion of course (I think many people call them nipples when they actually mean to say dimples because the words are so similar and they are not thinking about it at all --since language is dynamic this is actually a way in which it can change and the definition can change, but I am fighting that!) Spiked is what I see used the most, and to me it is more accurate than nippled, as well, but again I promise I will stop now, sorry again!