I don't have any problem with small plants establishing in the garden. I'm not one to fuss with them either. I plant 'em, then they're on their own. It's sink or swim.
I really think that starting with good, healthy plants is the key. Even tiny little ones generally do OK if they've had a good start.
Of course, I'm used to transplanting my wintersown stuff into garden beds at first or second true leaf stage- tiny! So something in a 3 or 4" pot seems big to me.
Karen