Bhoot monsters casting Paralyze III still cast after interruption

Date & Time: 09 July 2019, 18:26 PDT
Frequency: Always
World name: Hyperion
Character name: Cyrillo Rongway
Monster name: Gelid Bhoot
Class/Level: GNB 67
Area and coordinates: The Fringes, X:25.3 Y:15.2

Steps:
1. Engage a Bhoot type enemy in The Fringes or The Lochs.
2. Bhoot begins casting Paralyze III.
3. Interrupt Paralyze III with role skill Interject.
4. The Paralyze III cast bar shows the spell is interrupted.
5. The Bhoot uses Paralyze III anyway.

This isn't just a matter of latency. The cast time on Paralyze III is quite long (5s?). Even when interrupted within the first 25% of the cast bar, the spell takes effect seemingly as soon as the cast is interrupted. In other words, the spell seems to cast immediately in response to being "interrupted", rather than being canceled.