Why was the initial classification of 3I/ATLAS potentially questioned?

Initial data suggested an asteroid identification

There was initial ambiguity regarding whether 3I/ATLAS should be labeled a comet or an asteroid, largely stemming from observations made when the object was still distant from the Sun. When an object is observed far away, it may be too small or insufficiently heated to exhibit the necessary sublimation activity (outgassing) that reveals a coma or tail. If its trajectory is clearly hyperbolic (indicating an interstellar origin), observers might tentatively classify it as an asteroid until closer observation provides the spectroscopic evidence, or visible activity, that mandates a reclassification to a true comet.