I saw it too but it's too early to pass judgement on whether it's an error or not. He can switch between different levels. My first assumption was that he's standing in front of his enemies so it's probably not a good idea to expose his full powers, but he was flashing them his eyes to let them know he's a big boy so they shouldn't treat him like a baby.
God, we don't need to have another page of exposition in this chapter where the reason he doesn't show EMS gets covered. I was getting anxious with all the time spent on exposition and "catching up" because I wanted something to happen. I hope it was just the author figuring that people who have been following the comic long enough would be able to figure it out, because characters are always making sure not to expose their full powers until they're forced to or they want to give their foe a kick in the morale gut.