I have created a singleplayer creative world with only forest biome generation, where majority of the trees are oak trees. Flying around with xray didn't reveal a single pink log. Then I used JER (Just Enough Resources) profile command to scan ten thousand chunks of generaterd world to see if the pink log generated at all. No, not a single block of pink log generated in ten thousand chunks of the world with only a forest biome, where the majority of trees are oak trees. Either I got really unlucky with 1/10000 chance of a pink tree (Which is very improbable because every single chunk has multiple oak trees in it), or pink trees do not generate at all.
Same thing with normal terrain generation, with all biomes present.

I compared it with actual hbm on 1.7.10, where I created a world, and started flying around with xray to find a pink tree, and found it in the first few minutes.

Again, there is a possibility that I just got really unlucky, but please check if pink logs spawn at all