I spent a bit of time searching through this thread, but apologies if this has already been addressed.
If I book travel through the Cap One portal to earn bonus miles, does it code as a travel expense such that can I then use their purchase eraser to use miles to pay down the charges?
Or does purchase eraser only work with travel expenses direct with a merchant (hotel, airline, etc)?

For example, spend $1000 on a hotel booking through the Capital One portal, earn 10,000 miles.
Use those 10,000 miles to "erase" $100 from that charge on my next bill, essentially making this good for 10% off hotel and car rentals.