Thanks for supplying additional info.
'Guy' is wrong; the circuit has to be installed to meet the environment, and the environment is:
Z1 IIB T3
The fact that the device rating exceeds the environment requirement is pretty common as it's more cost effective (and less installation error inducing) for a manufacturer to make equipment to meet a more onerous set of criteria. ATEX certification carried out once for a hypothetical 1G (Z0) IIC T6 device is definitely cheaper than ATEX certification for each of 1G/2G/3G, IIA/B/C, T1-T6! Sorry these are now EPLs of Ga/Gb/Gc..
If the the environment was a Z2 IIA T1 and the device was a Ga IIC T6, would we go to the expense, time and effort of using barrier glands? No, of course not.
In summary, you have followed guidance correctly for the environment, device rating, cable type, energy potential and volumetric limit for the device within this circuit, so a non-barrier Ex d gland is appropriate.
I would also question the last time 'guy' had his CompEx refresher..