Missions expanding to lower paying missions

I have noticed the following missions expanding / spreading to lower paying missions

Medium Violent Protest- spreads to active shooter or Large Violent Protest, Active Shooter pays less and completely different units seems like it could be follow up instead of expansion

Large Violent Protest- spreads to Active Shooter, pays ¼ and completely different units, seems like it could be follow up instead of expansion

Shots fired at Officer – spreads to Active Shooter pays less.

Armed Foot Pursuit- expands to Shots fired at Officer that expands to Active Shooter and pays less that either of the first two

Large Natural Gas explosion – same spread as Natural Gas explosion – Full building collapse or Partial building collapse, Partial collapse pays less on the Large Natural Gas explosion mission.

It does not make sense to me for two of them but thanks for the reply.