Why snow is the real issue
A reception tent is a flexible cover stretched over a frame. For tents open to the public, the safety regulations require stability under the combined effect of normal wind and a snow load of 0.1 kN/m² on the horizontal projection. Keep in mind that snow is part of the structure's design, with a limited value.
This is the reason for the 4 centimetre threshold. Article CTS 7 provides for evacuation if snowfall exceeds 4 centimetres, insofar as build-up on the cover could not be avoided. In other words, what counts is not the depth on the ground but snow that has fallen without being cleared from the cover.
Other structures do not necessarily have the same limits. The only value that matters for your event is the one your tent hire company applies to its structure: ask for it in writing.