There is a Caro-Kann course on the GingerGM chess site that recommends this variation. They seem to think it is better than an early e5 for black. I don’t think the fantasy variation has been refuted, but it is probably fairly rare for a reason.
Caro Kann Fantasy Variation 3...e6 Best line for white
Sort:
Why would white play a3??
Nge2 or another developing move like Bf4 is more logical.
Moreover, 4.Be3 is another possible move.
https://www.chess.com/video/player/vasily-smyslov-master-of-attack-vs-gereben
Has the fantasy been neutralized?