Breaking the bottom of a stack of banners breaks all other banners instantaneously

The Bug

Breaking the bottom of a stack of banners breaks all other banners instantaneously.

Steps to Reproduce

• Summon a tower of banners.

  /fill ~1 ~ ~1 ~1 ~20 ~1 minecraft:white_banner
  

• Destroy the bottom supporting block of the banners.
• Take note as to whether or not banners all get destroyed at the same time when their supporting block gets destroyed.

Observed Behavior

Banners all get destroyed at the same time when their supporting block gets destroyed.

Expected Result

The breaking should spread from the bottom up gradually, as is the case with most other support-requiring blocks; instead, all blocks break at exactly the same time.