So I actually considered this topic in February, but it was brought up in the chat today and I said I'd probably post it, so here I go!
I think there should be a 5 - 20 minute window after upload or after the conclusion of an XHB where only the author of a song can upload a render. (An alternate version of this allows a longer window that the song's author or a mod could disable, should the author immediately know that they won't or can't render it themselves.)
I don't think it's typically done to snipe renderist points and is most often meant to be a helpful gesture, but intent doesn't undo the frustration I've seen in the past when someone wasn't ready IMMEDIATELY upon the end of compo and someone else was hovering above the refresh with render in hand. This could also allay potential guilty feelings of the prospective renderist themselves, since we'd have defined the protocol and courtesy for rending for someone else. I myself have occasionally felt strange doing MT32 hardware renders sometimes, since it's likely the final representation of someone else's song for most listeners after voting and for voting in majors.
The one point itself isn't a big deal, but I think that so long as it's not a burden to code of course, it's a worthy quality of life feature and favors the community aspects over the competitive aspects of this site!