Comparing fabric

The more I examine the tunics from stock, that the more that I get familiar with all the different materials, the more I start to notice how there are differences in what I would assume to be used and what is actually used. For example, the hair canvas that I have found in a couple of the tunics that you would assume to be stitched to the chest does not look like the chest canvas that I have sourced. when looking at it I wondered if this was mabye another type of canvas that I had not come across yet, however, the fabric actually looks more like a thick linen when I compare it to the Whaleys samples.

Linen has been mentioned a lot through my research as a layer of interlining, however it confuses me to think that it is used in the way chest canvas would be used. This leads me to think that there is no right or wrong way of constructing interlining fabric. There is not set fabrics that have to be used when interlining a tailored jacket, there are more options that you think. Or using linen in this fashion may be for particular types of tunics or from a particular era. As long as the fabric is doing what it is supposed to, then thats what matters. I suppose different tailors have their different preferences. It is hard to know whether I am right in saying this because I have unfortunately not some across a direct source of information yet which has led to this whole guessing game. I have ordered some samples for my folder.