Levelling dungeons do not have minimum ilevel. Would you think it was ok if your healer is in something like ilvl 25 gear? Since that's queueable as well.
Thing is, i270 isn't really low for any of the SB leveling dungeons. Like, at all. There isn't even really that much room for improvement before level 70.

What you're suggesting as a comparison isn't even remotely comparable.