Steps to reproduce difference 1:

1. Create items with triggers, and collect some value.
2. Navigate to Reports->Triggers Top 100
3. Uncheck all severity and click Apply. 

Result:
No data found. 
Expected:
All Hosts and triggers should be displayed. 

Steps to reproduce difference 2:

1. Create items with triggers, and collect some value.
2. Navigate to Reports->Triggers Top 100
3. Check 2-3 severity and press Apply. 
4. Click Reset button.

Result:
All severity is checked. All triggers and hosts displayed. 
Expected:
All severity UNchecked. All triggers and hosts displayed.