I don't think, "sex toy", would be a relivant term for Joi even from the she's not sentient point of view. This world is full of slavery, sexual and otherwise, there's no lack of access to sexual objects.

Joi AIs are a companion you can't have sex with in a world brimming with easily accessible physical sex bots. The sexualized marketing of Joi may be misleading as to the use of the product. People have used sexualized women to sell Coke, but that doesn't stop it from being carbonate sugar-water.

Having a digital companion be a digital girlfriend does certainly cross a line though. If you start gaming it out I really doubt a replicant would be interested in a digital "girlfriend" as a form of companion. It would be a label I don't see why a replicant would be interested in.

I don't think you're far off with Joi as sex toy exactly, it just isn't one. If you're simulating a "girlfriend" and remove sex and only simulate the relationship part, to label that a sex toy is to label all romantic relationships porn.