Marie Antoinette Caster Bond Dialogue

During the summer event, I was lucky enough to pull best french waifu, but upon actually using her I noticed after a while that I was leveling up bond but not actually unlocking the lines. I had her at ascension level 2, with bond level 5, and yet I only had the first two lines unlocked. Fast forward to this past lottery event, and I finally have enough spare experience to level everyone up, so I throw some her way and get her to ascension 3, and then check her dialogue. Lo and behold, bond 3 has unlocked. Get her to 4, and line 4 unlocked, etc.

Somehow, DW tied Marie's bond dialogue to her ascension level. Is this a bug, or a mechanic I've never noticed before? I've gotten other servants in the past up to bond 5 before max ascension, and they've all worked properly.