Red and Brown Mushrooms spreading is incorrect

According to a change introduced in 26.3 Snapshot 1, Red and Brown Mushrooms can now be placed on any block with a solid top face, regardless of the light level. They can also spread to adjacent blocks if the light level is below 13, or if their supporting block overrides the light requirement.

However, my recent testing revealed that Red and Brown Mushrooms do not appear to spread to most other blocks. In my testing, they only spread to nearby Mycelium, Podzol, or Nylium.

I tested this by building a small enclosed room using tinted glass and placing various blocks on the floor around a mushroom positioned in the center. I placed a Grass Block in one corner and Mycelium, Podzol, and Nylium in the opposite corner, then monitored the mushroom's spread.

As shown in the attached video, the mushroom spreads to the Mycelium, Podzol, and Nylium, but does not spread to the Grass Block or the other tested blocks, despite the light level being below 13.

This appears to contradict the change introduced in 26.3 Snapshot 1, which states that mushrooms can spread to adjacent blocks when the light level is below 13, or when their supporting block overrides the light requirement.