Uvaria rufa seeds look like typical Annonaceae seeds, small and brown, like a smaller version of cherimoya seeds. No resemblance to guava seeds.
I've ordered Uvaria rufa seeds from three different online sellers, including Trade Winds. All the seeds looked the same. All performed the same. Universally atrocious germination rate. It could be that all the seeds were old and bad. It could be that this species naturally has a poor germination rate. I'm also willing to believe I did not germinate them properly; though I'm not sure what else I could provide them other than what I gave them: seed starting mix, a plant light, a heat mat, and regular mistings of rainwater.
However, I've noticed that some plants from hotter, more tropical regions, seem to germinate better with a heavier soil mix. I discovered that fact with rambutan seeds. I failed to germinate them a couple of times using the standard method described above, so I gave up on germinating any grocery store rambutan seeds and started throwing them all in one of my compost buckets. Lo and behold, the bucket was full of rambutan seedlings in very little time, in heavy, wet, pure compost with no attention paid to them whatsoever. I might try a similar method with Uvaria rufa, if I'm foolhardy enough to ever order any seeds again.