I assume people looking for co-founders aren't looking to "date" candidates for months/years and therefore delay raising/launching for a substantial period of time, so it's more like marrying someone you match with on Tinder after what can only be a cursory familiarization. Could be my own bias coloring that perception, though.

If they're looking for cofounders, their product could be at any stage, including not-even-started. Raising may not even be on the map yet, or ever. Maybe you want to find a co-founder who wants to bootstrap exclusively.

Maybe you want to find someone who's a good culture fit with you, and do a small project together. If it goes well, keep going, if not, stop there. So it really is more like dating than marrying.