Nothing you quoted invalidates my point. PHB doesn't say it's not flammable, it has historically been flammable, and people don't follow/agree with Sage Advice. Simple as that. It's not a BG3/PHB difference, it's a BG3/Sage Advice difference.
Plus, if we followed the Sage Advice reasoning, there are a TON of things players and DMs pull that are "against the rules" because he's taking a 'only things clearly defined are allowed' stance in this instance when it's not taken in any other instance. Can a player recover caltrops? The PHB doesn't say they're "recoverable" so the Sage Advice logic says no but a practical application would be that of course a player could spend 5-10 minutes picking them up.