My theory is that they were given all the scenes disjointed, which made it impossible to see the larger context.
Yes, it's a writing and scripting collision/oversight isn't it?
If we follow the path where Tav actively romances Halsin and Shadowheart together it starts with Halsin declaring his interest and asking Tav to speak to Shadowheart first. Shadowheart alludes to being understanding of Tav's desires and "wants all the details" afterwards. This properly foreshadows what Shadowheart says in the brothel scene because Tav has now given Shadowheart a spicy and juicy recollection of their time spent with Halsin. Tav and Shadowheart proceed to take their relationship the next step and then the flirty banter happens in the context of Tav, Halsin and Shadowheart having a fully consensual agreement about their poly relationship. It all checks out.
But when bad writing/scripting causes this path to get mixed up with the path where Tav has shown no interest in including Halsin (or worse, actively rejected him) it instead just becomes creepy, cringey and toxic.
