Tanks have often been modified for special purposes. The most common is armoured recovery vehicles, used during combat for recovery or repair of battle-damaged and inoperable armoured fighting vehicles. Another common use is to provide armoured capability for combat engineers. These include tanks carrying large-calibre demolition guns, with flails or ploughs for mine-clearing, or flame tanks armed with flamethrowers. The tank occasionally may lose its weapons and the chassis alone may be used, as in bridge-laying tanks
https://en.wikipedia.org/wiki/Tank_classification#Specialist_tank
The chassis of tank models have been repurposed for other tasks, yes. That doesn’t make those armored vehicles tanks.
I mean, everyone but you classifies them as tanks, but ok.