My suggestion is that as your SOMM has no definition go to another and see what that says. Do a trawel through all the SOMM you can find and see what they say.
If the majority says columns are measured floor to floor as you are hoping you have a reasonable case to advance that even though your SOMM does not define it, normal practice dictates that it should be measured thus.
Something along the lines of contra preferentum

good luck

Can I make a suggestion?
Consider the formwork, measure the formwork for the beam and the concrete and re-bar contained.
Do the same for the column, in other words measure the beam from face of column to face of column. The column is measured from top of slab to top of slab.

I am only a mere planner with no QS training so I may be barking up the wrong tree.

Hernan,

Usual computation especially if beams width is larger than thickness of column when it crosses the method of measurement should use a beam rate. It is also clearly shown on the drawing that the beam number/name or beam tag number is the same after crossing the column. You can make an argument by showing the detail drawings and rebar schedule. Lintel beam are normally end from column to column and the column rates prevails. Maybe you can use the detail drawing as reference. Column name or column tag number change on every floor or levels. There should be a heavy civil or building pagination that you can use as another reference. Strange to hear that does not defined in your contract method of measurements especially on bulk quantities that you mentioned.

Rodel