Very little I would have thought.
Yes it will expand but it won't be much at all over something the length of a knife between the temperatures of a cold wotkshop and body temp which is about the maximum it would be used at.
Even taking the differing linear-expansion-coefficient between wood and metal, its not much.
The timber getting wet and or drying out will make a far bigger difference IMO.
I wondered if anyone would go down this particular road.
What about the
rate of expansion/contraction/recovery ?
Steel, brass, copper, and different types of wood et al - they all shift different amounts (doesn't really matter how slightly - it can still be enough to shear a glue joint which, by definition, is not meant to be stressed in that fashion) and, more importantly, they all move or recover at very different rates.
Let's say the tang shifts a tiny bit, the scales shift a little more, and the bolster or guard somewhere in between.
That's got to hammer any epoxy joint's capacity to remain intact if the materials joined are moving a bit.
Especially if the materials also do their own thing at different rates/speeds.
I think we're talking about very real contributory factors here rather than individual sole cause.
I'd put money on the scales being cut from large blocks and used without leaving them to settle for many months. My own rule of thumb is cut the scales to just oversized and let them lie for 6 - 12 months minimum. A few years is better if you can arrange it, but that's hard to achieve when you're cranking out 30 knives a week and is in no way meant as a criticism of SWC.