Since London Service Portal, a variable help text is shown immediately below the variable identifier name, above the variable entry field.

1. Login a London instance. 
2. Configure any catalog item with a variable that has 'help text'.
3. Open the catalog item in Service portal. Notice the help text populates immediately below the variable identifier.
4. Login a Kingston instance.
5. Repeat steps 2-3. Notice the help text populates below the variable content entry box. 
   
   

This is expected behaviour and by design since London, due to a redesign to align with the platform behaviour, occurred as part of the fix for PRB1190937/KB0656295.