I don't think there is anything obligatory about having this kind of discussion with your therapist. You might see it as your business and not something of their concern. However, it might be that speaking about it would give you more information about your relational patterns/emotional states/aspects of self. For example, is there something to explore about those parts of you who don't feel expressive or competent enough to write a meaningful card without borrowing words from elsewhere? Or would it be useful to look at what happens to your experience of intimacy when you use an external tool? What feels compromised or facilitated and so on? Personally, I probably would discuss because it would point some important relational aspects for me, but you might not be working in that way. YTMV. Your therapy may vary! Look una, I have invented new Gen Z speak! Comrade on the cutting edge as per.