I think the main thing you guys are missing and what makes Teoscar and Grichuk so similar is that both can absolutely crush baseballs. For both it comes at the expense of consistent contact, but clearly they're the type of guys the team loves. Teoscar hits baseballs VERY hard, he strikes out a lot but ostensibly not Joey Gallo level, walks enough to not be Kevin Pillar at the plate, is clearly a plus runner and it would be surprising if his athleticism didn't translate to average defense at least. All of those to me sound like the qualities of an at least average MLB regular, where in seasons that he can manage to cut the swing and miss rate he can be a very valuable contributor.
I just don't see the argument for why they're so different, yes Grichuk has proven to be a good defender at the highest level, but it's not like Hernandez has shown that he's clueless out there. I think they're very similar players, one just happens to have a longer track record which is obviously valuable for assessing what kind of player he'll be going forward at the MLB.