It's part of the process the Guards use to get the all over shine they have for parades. They burn the leather with a hot spoon and melt the beeswax on. This makes the leather very hard and not at all flexible. It's a completely irreversible operation... though if anyone knows how to fix it, it's Chomley-Warner on this forum.
This wasn't generally done to boots in WWII and the shine in WWII would only be on the toecap and maybe on the heel. Though official rules said that the boots should be shined to a good shine on the toe it's a fallacy to say they said they should shined to a high shine like modern guards boots and definitely not all over.
The toecaps of boots could have been burned in WWII by some soldiers, but officially it was a banned practice as the boots lose their waterproof properties once it's done.
Yes it may do... it can also make them almost unwearable.
I've had two pairs of guardsed boots. One was wearable and got a lot of use from me, the other pair was completely useless and so hard it was unwearable. Luckily now I've got several pairs that have never been touched by the guards.
For airsoft anklets/gaiters/putties over modern boots are fine, also for airsoft rather than ammo boots you could get DMS boots, (that's what I wear for airsoft), which look the same except for the soles, as for comfort I find both DMS and ammo boots comfortable, (I wear ammo boots for living history events), the thing to keep in mind with ammo boots is they can be a bugger to control on hard surfaces, lots of slippery hobnails 
Aye DMS etc are great in the field - but for that fabulous crunch crunch ringing sound walking across tarmac/ roads/ the enemy you cant beat ammo boots!
I'm a hero with coward's legs.
