couple of points here –
the worktop will expand/contract slightly over the course of the year as temperatures/humidity changes.
If it is too tight between the two taller units, it might bow/deform as the extra material needs to go somewhere.
is it going on top of a 1200mm unit? have you measured the unit? is it exactly 1200mm?
If you worktop was exactly 1200mm (the same size as your gap)would it be possible to drop it into place without scratching the side panels either side??
to be honest, as an ex-kitchen fitter +/- 4mm doesn’t sound too horrific.
However, your piece of worktop may have been cut on some sort of CNC machine, which can cut to less than 1mm tolerance – so I reckon the 1196 size is deliberate.