The writers needs to validate their heat probe when it comes to measuring Jassi-Armaan heat. Writing supported by statistics would be more acceptable.
In my opinion, the heat generated by Jassi-Armaan is so much that it wud turn the needle of the heat probe 360 deg displaying a sub zero reading. So it cud be that without doing a research the writer categorized Jassi-Armaan as endothermic (cold) instead of exothermic.
Looks like Jassi-Purab heat was measurable as it was within the range of the probe. However, it casts doubt as the writer based her reasoning on the appearance of the characters (both wear glasses).
Lastly, I do agree that the heat generated by ugly jassi and Armaan would have melted the probe completely...the needle would have gone round and round till the probe completely malfunctioned. But, the writer calling Jassi-Armaan chemistry deadwood is certainly unacceptable.