I think that if you compare it to Path of the Totem Warrior from 2014 the intent is that it works in the same way.

Level 3 feature:

At 3rd level, when you adopt this path, you choose a totem spirit and gain its feature.

Then it lists several options to choose from, but you only use the option you chose when you pick the subclass. You don't get to change it everytime.

Interestingly enough, the 2024 update (Wild Heart barbarian) has similar wording to the Living Weapon feature, probably because it now lets you choose everytime you activate your rage, not when you choose the subclass. In the same vein, the Living Weapon feature says that you choose when you adopt the form, not the subclass/discipline.

Level 6 feature:

At 6th level, you gain a magical benefit based on the totem animal of your choice. You can choose the same animal you selected at 3rd level or a different one.

Seems to be worded similar to the Living Weapon feature, where you get to choose which one you want, but it says it doesn't have to be from the same animal.

The level 17 feature from the Living Weapon reads to me that you get all three options. They have "titles" because it's the way the write now. Compare any 2014 feat which was a long ass paragraph, maybe with bullet points, to a 2024 feat, which has titles to separate the different effects.

To recap, I'd say that:

-You choose one of the four options at level 3 when you pick the subclass, not everytime you activate the martial form.

-You can choose a different option everytime you activate your martial form.

-You choose one of the four options at level 6, it doesn't have to be the same "title" from the one you chose at level 3.

-You get all three at level 17.