X series ISO Inflation

Highly likely - the actual path of light through a lens can differ ... even in the same 'family' of lenses.

Zeiss famously uses T-values on it's lens products - a T value of F2.8 for example is the true physical transmitted light value ... not the mathematically 'calculated' f2.8 value of many other lenses.

Metering methods/technologies, light transmission through lens - even the differing values within a scene - can all affect the so-called 'correct' exposure.