Its unclear what the intended behavior of the Explosive Flask node is, but the behavior and description do not match.
The tooltip description says “Acid Flask’s base damage is converted to fire damage and its hits deal significantly more damage (multiplicative with other modifiers). Consequently this damage scales with increases to fire damage, but not increases to physical damage. Acid Flask can no longer apply poison or create poison pools.”
However when you take the node the skill actually maintains its physical tags, and instead converts the flask’s poison tags to fire tags. The summary blocks also say “Physical → Fire Damage”
This wouldn’t be a huge deal, but it does technically imply that you could take both Explosive Flask to convert the physical to fire, and use an item to convert the poison to cold damage, and you definitely cannot do that. If this is functioning as intended then the bug should be easily fixed with some text updates.
I’m not supplying a log or screen grab because this is trivially easy to check/reproduce, and is likely more of a human error in writing tool-tips than it is a proper bug.