I've always gotten the feeling that MHJ liked f(x) the most out of every group she worked with at SM. Not just because her and Krystal were close but because out of all her projects you can see New Jeans the most in the artistic direction of Electric Shock, Pink Tape, and 4 Walls albums.
I can see her thinking that one day she will make a group of her own like f(x) but will have 100% control over everything instead of just art direction. She could have made a boy group instead but didn't.