Yes. I think this is less a tantrum, and more of a "fuck you" from Smirnova to Kharlan, but your interpretation is fine.

The rules state that the competitors must shake hands at the end of a bout, and that the penalty for refusing to shake hands is a black card. At the beginning of the pandemic, this rule was suspended, and was replaced with saluting and tapping blades. It is not clear whether the handshake rule is back in effect at the international level (which in itself is a huge problem - if athletes can't look up the rules, it's hard to follow them).

As an online observer, these are the facts I was able to gather. At the end of this bout, Kharlan offered her blade for the blade tap, and instead of reciprocating, Smirnova offered her hand for a handshake. Kharlan then left the piste without tapping blades or shaking hands, and Smirnova launched her complaint which (per the rules) required her to remain on piste until the issue was resolved. The officials decided the complaint was legitimate, and black carded Kharlan.

All that follows is my own speculation. Kharlan offered the blade tap but was refused. Depending on whether the handshake rule is officially reinstated (and it seems that many athletes at this particular competition were just tapping blades without a handshake) she may have been able to lodge her own complaint that Smirnova was unwilling to tap blades. They could have just had an old fashioned stand-off, with one fencer extending their blade for the tap and the other extending their hand for the handshake, neither willing to compromise, and it would (probably) have resulted in the referee clarifying the rules without penalty to either fencer. But because Kharlan left the piste without tapping blades and without shaking hands, it left an opening for Smirnova to exploit.

I do wish that the FIE would go on record saying whether the handshake rule is fully back in effect. I'm actually a fan of tapping blades, because too many fencers show up to tournaments sick, and shaking hands with everyone is a good way to spread disease. Even beyond that, people often have very sweaty hands, and it's just kinda gross.