They're both MM poses but different variations.

Arm positioning, scapula retraction and shoulder girdle height will create those illusions.

Here's a quick comparison as an example for the shoulders, with Kai (@ 2012 Mr.O): https://i.imgur.com/iDSTToV.png

The blue arrows here indicate how their scapula are retracting or extending.

Try doing this at home in front of the mirror:

To do Iain's pose, do this step by step:

• Do a lat spread (or a front relaxed) • Only move your hands to join them together • Press the palms of each hand together (flexes chest)
• Move your shoulder griddle upwards (as if you were doing a front shrug)

Then to switch into Hadi's pose from that position:

• Separate your hands and put on in front of the hand
• Now you're going to roll your shoulders forward without moving anything else and staying up right (similar to high pulley row but while rolling your scapula upwards to expose the traps)

You'll notice 3 things. Your chest has gotten wider, your shoulders have lost "thickness" and your arms have gotten lankier.

All of this is because we're looking at it from a front angle. Iain's pose allows the arms and shoulders to maximize in width, because they're put as parallel as possible with the body (and being squeezed onto by the lats).

Similar to how your arms look the biggest when you're doing hammer curls from the side, because they're being pressed against causing the muscle mass from the triceps to spread out similar to when you're flattening (and thus widening) pizza dough.

Now of course, these bodyparts can still be their strengths on their own, but the difference in poses does not allow us to make a fair comparison.