Fear the Walking Dead did have a crossover within Season 2, only it was with the mini-miniseries Flight 462, which aired during commercial breaks for The Walking Dead Season 6.
Fear the Walking Dead lost some characters at the midseason break, and divided up those that lived.
When Fear the Walking Dead was first announced, not much was known beyond the fact that it would line up with the beginning of the zombie apocalypse, making it a temporary prequel to The Walking Dead.
The same hasnt quite happened for the characters of Fear the Walking Dead, and Erickson understands that some fans have been quite critical of the companion series arguably slow-moving approach.