Manifold Stud/Washer Question

[Babalouie]

Before I took apart my engine, I saw that there was a mismatch between the exhaust manifold flange and the inlet manifold flange (you can see in this pic that the "bridge washer" is not sitting quite flat):

 

My motor was showing signs of a vacuum leak somewhere so I figured that maybe this was preventing the inlet from sealing properly on the head.

 

The difference is a tiny tick over 1mm, with the exhaust flange being thicker...so I figure that I'll do the right thing and get the header flange milled 1mm so that it's the same thickness as the inlet, and so the "bridge washer" can sit flat.

 

Now the thing is...the machine shop is saying that the 1mm thickness difference is just fine, that new bridge washers:

 

 

...have a concave surface on the bottom and the outer ridge will "bite" into the high side and all will be well.

 

 

Does this sound right, L-series experts? I can see his point, but at the back of my head I'm thinking there is no reason not to mill the header to the same thickness as the inlet...