By definition, when food service and walking are difficult, turbulence is moderate. When food service and walking are impossible, turbulence is severe.

The degree of turbulence is subjective, however; what is moderate to one person maybe light to another, severe to another, and cabin service ordered stopped and flight attendants seated isn't necessarily a function of severity, but prudence, on the part of the crew. It's possible that reports or forecasts of turbulence were significant enough that while walking and service might have been possible, the captain decided to seat the flight attendants out of caution.

Without having been there, of course, it is impossible to say what the origional poster experienced.

The definition of moderate states that occupants feel definite strains against seat belts or shoulder straps, and unsecure objects are dislodged. In the case of severe turbulence, by definition, occupants are forced violently against seatbelts or shoulder straps, and unsecured objects are tossed about. That may help determine what was going on in the cabin, and the actual level of turbulence.

https://www.faa.gov/air_traffic/publ...tml#Tt93b6ROBE