I noticed you have all the tickets for this bug marked as resolved.  But it is not fixed, it is happening right now!

Spiders are spawning on a 1-block space, specifically in my Creeper farm.

I was recording this on video and I will provide screenshots.

My Creeper farm uses platforms with this pattern: block->block with button on it->block->block with button on it, and hole in between, repeating! With trapdoors overhead. So the only spaces for a mob to spawn are 1-block!

See the images I have attached!