A hostile mob spawns in the area where the Scaffolding has been set up.

Observed behaviour

• Hostile mobs do not spawn in spaces where glass or similar materials were originally installed. However, they do spawn in the case of scaffolding.

Expected behaviour

• Ideally, this would be a feature rather than a bug, as it is very useful for transporting mobs in Mob Farm. However, according to this specification, when I place a scaffolding, hostile mob spawns cannot be stopped.
  Was this specification foreseen?