Ah, that's less bad than I guessed but still pretty bad. Caucus should not just be your union rep, it should include others on your BC as well and anything TA'd should be 100% known and agreed to by the whole BC (or if necessary, a vote by the BC, but functional ones usually reach consensus). It feels very shifty that you're TAing things that you technically don't know the content of. And the decision to TA at all is a big one that must be done strategically - you'd want to get the stuff you don't really care about TA'd early so that you can emphasize the brass tacks at the end - the things that matter to your coworkers. Usually this is pay, benefits, and key issues of working conditions that you organized around before bargaining. The hybrid work issue sounds like one of those. You want to emphatically reject that if you think you can mobilize around it.
Your union rep is being weird to say that some issue important to you all is something the company won't go for. The power to get your demands doesn't happen at the bargaining table, it's in your ability to mobilize your coworkers to take direct action, including actions leading up to a strike, the strike itself, and escalations during the strike. If that issue is one you think you can use to motivate and rally your membership, then you should keep it on the table. If you think it would be very difficult to get them to care, that's when you can do an early TA, seeing how much you can get through bluffing and then just TA anyways.
So if your union rep isn't focused on what you can mobilize around and what your membership cares about - and thinking about how you'll include this in the inevitable need to strike - they're incompetent or worse. They may even be bargaining against you, in effect. I would start thinking about what to do if the rep begins trying to avoid striking. That is something that a milquetoast union will often do because they care about having to cover strike pay and have opted for a strategy that is more collaborative with the employer. In that case you will still need to create a parallel organizing campaign.
If I'm correct that it's just the union rep who's got the power to TA right now, I recommend changing that ASAP. Stare that you all agree that a worker must be present and collaborating. Use the fact that you all don't even know what's in in your TAs to make this demand. If you present it as an expectation / entitlement, like "we discussed this and this is how it will work going forward" you may be able to change the dynamic more generally. Of course, do all of this calmly and in a friendly way. This is probably the most impactful thing you could do right now aside from holding organizing meetings with your coworkers to discuss bargaining and to get a sense for what matters to them most. You want your coworkers to know you're on their side and to not be blindsided by anything alienating them from you when it comes time to ask them to strike. The worst case scenario is that they say, "what was the point of unionizing if this is what we get?" You can head that off through transparency and involvement. People that seem concerned can be onboarded through direct conversations and inclusion on the BC, assuming you don't have any bylaws preventing that, for example.
So getting into that room and making TA decisions together is essential and so is creating the contact, trust, and involvement of membership in preparation for your primary organizing campaign (BC bargaining and strike) and any parallel campaign that you may need to run from behind the scenes eventually.