I hear you. Being near pine (as in the shelves or lid) is different from being in pine, as in laying in or on sappy pine shavings. So absolutely no problem with pine as a building material for supporting cages.
And the rambles..
Kiln-dried pine shavings are likley no worse for your snakes than any other wood product. I say this only as someone who used pine for many many years with very long-lived snakes on it. Yes pine does contain those nasty phenols, which in high concentration in limited ventilation are not good. But dry pine shavings have very little of the chemical left in it. I suppose with alternatives like aspen and hardwood chips, there is no need to use pine. These products use marketing to their advantage and lead the consumer to believe that pine is not safe. Pine oil is not safe. Dry pine wood is fine in many cases.
Glass is inert. But think about all of those enclosed rack systems with plastic boxes being heated from below. I wonder how many bad chemicals are released from that? At herp-related temps, perhaps the amount is negligible. The substrate probably traps most, but still the discussion is interesting. Pick your poison I guess. I have moved to FDA-approved plastic boxes (polycarbonate) that are considered safe when heated to 180 deg F. Much more expensive but are also far more durable than the typical storage box.
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Mark