Igloo Basement Generation Error

Whilst playing the latest snapshot survival, I found an igloo and decided to enter the basement to loot it. When I got to the bottom, I realized that the spots in the wall where the villager and zombie villagers usually are was replaced by stone. I can still hear the two of them, as seen in the attached screenshot with the subtitles. I may be mistaken that this is intentional, but I thought I best report it anyway. Thank you.

 

Edit: I found the villagers, they were about 3 blocks up into the ceiling above where they were meant to be.