I seem to remember in the past whenever they released a 5* through an event with a dedicated token that the odds of getting a 5* still remained at the 15% for normal legendaries, just all on the one character. The thanos tokens only have him at 10%. Maybe I just assumed this was the case and character specific tokens have always been at 10%? Pretty decent reduction in value of the token. . .
Single 5* tokens have always been 10%.
The last two special tokens: BW (Red Room) and Strange (Sanctum Sanctorum) both gave a 10% chance to earn their 5* covers.
I guess what they say about assuming is true. . .
Even the Civil War tokens only gave a 10% chance at IM or Cap.