Op amp advertised as BW = 105MHz, but GBP is actually 70MHz, what's being spec'd differently?
Not sure if this is the op-amp you are referring to, but the OPA2810 typical characteristics contain similar numbers.
Interestingly, perhaps, the typical unity-gain bandwidth of the amplifier increases from 75MHz to 105MHz (typ) when the capacitive loading is increased from 4.7pF to 33pF as it makes the amplifier less stable and there is some gain peaking near the cutoff.

At higher gains (+11), with 4.7pF loading, the typical gain-bandwidth product is 70MHz, which is pretty close to the 75MHz unity gain bandwidth with 4.7pF loading.