That's routing though; BNA-ASE is via BNE-HOU/DEN/CHI-ASE. I'm fairly sure inventory will pull the through-inventory rule if the connection is short enough to ordinarily count as a transfer (4h00 domestic or next scheduled flight) or not otherwise (regardless of fare rules). You might be right that the fare rules on SFO-YYC actually auto-price like "up to 12 hours, no stopover", just a weird wording. That does seem to be how the computer does it. My original point was that there is no inventory marrying rule for the >4h00 connections on SFO-DEN-YYC because that part of the computer thinks it's impossible to price on a single fare. The fact that assumption is wrong is the whole reason why the situation in the OP came up.