Event boosted drop rates are capped at 75%?

[The Secret Cow Level]

Ancient Guiding Stones have a normal drop rate of 45% in the middle section (Endorim Temple) of Lakrum. (30% at the left and right sides. 0% near main town / Mirash. No Energy of Repose. No Prestige Pass).

However with the double drop rate event, the Ancient Guiding Stones at that area is only 75%, and not 90% as assumed. (518 mobs killed in Endorim Temple of Lakrum, 391 dropped.)

Drop Rates with 2x drop event for Endorim Temple: (No Repose, no Prestige Pass)

• Ancient Guiding Stone: 75.5% (391 / 518)
  • Base rate: 45% (Long term observation)
• Legendary Guiding Stone: 27.2% (141 / 518)
  • Base rate: 13.5% (estimated)
• Ultimate Guiding Stone: 19.5% (101 / 518)
  • Base rate: 9.75% (estimated)
• Level 60 Ancient Manastones: 1.2% (6/518)
  • Base rate: 0.6% (estimated)

[Lapis-DN]

maybe its a hard cap to every drop? I don't know.
I got 3 daevanion skills out of 3 red shugos with Berdin Drop + Server Drop boost

 

but i think the drop rate was something around 75% too