Yes, they do mean and enforce both sides of the aisle can ONLY have one lap child. That would be on a 737 max of 6 passengers in seats , 3 on each side and one lap child per row. Can't have 2 lap children in the same row even across from each other.

Problem is besides the FARs, every airline has their own company rules. Which may differ from company to company. Some have a rule that electronics must be turned off before the door is closed. Some after the door is closed, but the aircraft can't move until all are turned off and stored. People fly on different carriers and expect the same rules and it doesn't happen.

As a general rule, just do what the employees say. In 99.9% of the time, they are following the FARS or company rules. They don't make up this stuff for fun.