In latest version, I have noticed that iron golems seem to spawn outside the normal boundaries as described by the wiki and as I have experienced myself through two years of playing.

More specifically, they spawn at places that are higher than 2 blocks above village center and more than 8 blocks away from village center.

To reproduce:

Create a village with 20 beds, 10 workstations and 10 villagers. Observe as the villagers connect to beds and workstations. For observation purposes, village must be constructed in a compact manner. Make a solid roof over the village, leaving a gap with 2 blocks of air between floor and ceiling, allowing villagers to roam inside the enclosed area but no golems to spawn there.

Observe as an iron golem spawns. Kill golems if necessary for new ones to spawn.

Expected results:

Golems spawn within a boundary of 8 blocks from the nearest possible village center (bed or workstation) and not on the roof, because the roof is 2 blocks above any possible village center.

Observed result:

Golems frequently spawn on the roof and at points farther than 8 blocks away from any possible village center (bed or workstation). Even adding another layer of blocks to the roof does not prevent golems from spawning on it.

Note that this apparent change may be beneficial to the player, as it allows iron golems to spawn on the rrof of a village, increasing the effective area where golems may spawn and be caught in a water stream for iron production.