I think Fernandes should have been sent off, but the standard 3 game suspension would have been sufficient in that case. He makes unnecessary contact with a match official and with some force, but to a lesser degree than Mitrovic.
If Fernandes had been given 3 games off and Mitrovic now gets ~10 games, that would have looked like taking both incidents seriously, while also still acknowledging the difference in aggression between them.
Unfortunately, because Fernandes was missed, I worry that 0 games for him and 10 games for Mitrovic will feel like too big a distinction to make between two incidents that were in reality, not miles apart. Which means rationale exists for them to bottle it and only give him the standard suspension or a very small additional punishment.