I would define "just spanking" as being struck on the bottom with no scolding or discipline dynamic, simply because one enjoys the sensation, pain, or connection. What is termed 'fun' spankings would be in this category as well. I don't enjoy these things at all, in fact I hate it, so I definitely don't see it as fun.
Does this mean that I'm not a spanko? I don't know...maybe. I guess you could say that what I have is really a discipline fetish and not necessarily a pure spanking fetish. I'm always fantasizing about being disciplined in some way: scolding, lecturing, spanking, writing lines or essays or being grounded. This can be real discipline or 'funishment'...as long as there is some sort of reason. Don't let one of these things happen in real life because I will obsessively think about it and replay it in my mind endlessly. Occasionally my psychiatrist will lecture me and boy do I eat that up.
I'm not really sure why discipline makes a spanking more bearable to me, it just does. I suppose it may be due to the headspace it puts me into. I'm getting it for my own good, to make me a better person, etc. I think it's also the feeling that I'm being loved and cared for.
Moving forward I will not bottom to somebody who just spanks. If that is your style of spanking I won't bottom to you. It's not fair to myself and it wouldn't be fair to the Top either because (mostly) all Tops want their spankee to enjoy the scene just as much as they are. I know this greatly limits the amount of play and play partners that I have, which does suck. But it's for the best.