Maybe you're too young to remember Eric Lindros but he was more skilled, more tenacious, more understanding of physical hockey than Slafkovsky and his career was derailed due to his inability to be "more aware of the danger, keep his head up and watch his blind spots".
Lindros had incredible stats and in the dead-puck era and was a physical specimen, so it isn't a fair comparison to Slaf who will likely never be as productive or as physical but it's worth noting the downside comparables of rushing someone to the NHL who is not capable of keeping up with the physical threats around him.
Slaf was behind the play against Vancouver, as usual, because he's not NHL ready. I think I was wrong to say that he needs more minutes -- it's clear MSL is trying to protect him and bring him along slowly for his own good. Maybe it'll work but I don't see the point of rushing a skill player to the NHL to play garbage time next to scrubs and struggle when he plays in a scoring role. He wasn't too good for Liiga just six months ago so it's not like it's a surprise he's not keeping up with the NHL.
I doubt this was the concern. I think they thought he was too good for the OHL and the AHL option was no better than the NHL option (+MSL effect) so they ignored the fourth option: Europe. In any case, we'll only know by the end of the season if Slaf has really developed his NHL-game or not.