honest answer is I don't know, however providing you use a spray on it shouldn't affect them - spray on sits on top of the fabric and forms a shell over the garment, unlike wash-in which sits in the material.
that said, if you're going for Spray On, try and get some Grangers Super-Pruf, it's proclaimed (by the experts) to be better than Nikwax. I use Nikwax for footwear and Grangers for clothing, and had have never had an issue.
That webbing is truly old school. Haven't seen Olive Drab webbing since 1996. Where's the Photo from? Brecon/Falklands/Norway? Assume since you were cutting around in Arctic you were the dicked Arctic Support Reg for NATO forces Norway.
That wasnt mine, we trialled plce in QRF coy at Kellys Garden in 1985. As I was an 84 man I had an smg so I took 58 pattern. The PLCE was gash, wouldnt hold together and pouches were no good for SLRs then!
Mine is on the left next to me!
Oh and the dog is Sampson when he was about 10 weeks old, he is about 5 now and a cracking dog.
Always found the windies great out of the box. If you wore them without washing them then they seemed to stay pretty showerproof. Eventually getting that sheen of oil, grease and dirt that is in itself a waterproofing agent ! Much as in Ugly's very Ally photo.
If you keep washing them they stay windproof but loose the showerproofing.
Mind that was the gaberdine ones I'm talking about and not that cr@p they seem to have been issuing since the 90's.