There are several issues here;
1. The sculpting of the Master Figures, the most recent Airfix 1/48th figures leaves a lot to be desired, they are of questionable proportions and the poses are over emphasised. The best sculptor who worked for Airfix was Ron Cameron who was responsible for many figures including the Multi-Pose series. His figures have a natural stance and are in proportion.
2. Scale, this is open to interpretation and not all sets of figures keep to the same standards, resulting in some figures being either much smaller or larger than might be expected even allowing for the variations in height of the Human figure. I have always assumed that scale is measured from ground to top of head.
One issue with injection moulded figures is that in turning the original master into the metal moulds then this is where errors creep in both with the straight forward setting to the correct scale on the pantograph/CAD copy and also the allowances made for plastic shrinkage.
3. Fitting the figure to the model. If the figure is aircrew it's pretty straightforward modelling the 'Master' standing and then flight suits etc just hang naturally. However if the figure has to fit into a cockpit then in real life this is tight fit so any kit the crew member would be wearing is distorted out of shape.  I'm sure the same can be said for figures in armoured vehicles and manning guns etc. I think sometimes the manufacturer doesn't like the figures to look too misshapen and creates a figure that looks as though they are just sitting on a Park Bench.
4. It's just a last, and not important part of the kit as far as the manufacturer is concerned so they just go with what is easiest to provide.

As an aside I have read that perhaps Airfix could use LIDAR scanning of re-enactor's for their figures. Not sure about that, as many I've seen are not really representative of the younger, slimmer real life aircrew and soldiers they are trying to portray!!

The internal windscreen armour is held in place with just 4 small attachment points and with the Gunsight fitted in front!!! of the armoured screen it makes for a tricky fit that has to be well fixed before committing to attaching the screen.

Here we are, so far!
Just about to mask up ready for airbrushing OD top surfaces.
Only issue the windscreen and internal armour fit.

What about a few pedal bins?

It’s fair because the 3 quite sizeable ball bearings are included in the kit! I haven’t come across any other kit that includes feature. Tamiya have, in the past, provided cast shapes for balance weights.

House Points to Kevin! It's the Tamiya white boxed kit of the P38H.
Super kit but you have to follow the instructions carefully as there are quite a lot of alternative parts which need sorting, ie 3 instrument panels!

Sorting through items cut from past modelling magazines, this photo inn SAM May2007. Our stand at the Doncaster Air Museum model show.