When WT takes you above your “base” maximum- 150, 162, whatever- you can see your Fury bubble drop a little. It’ll do this several times.
Basically, WT seems to “unlock” a new segment of Fury bubble, in several stages. Once you’ve entered the next “segment” you can actually fill the bubble the rest of the way with other forms of Fury generation (Charge, shouts, etc).
Starting with a Fury bubble of max 150 (100 base + 50 paragon) I saw 4 additional segments, that cap out at 200, 250, 305, and 350.
Video:
