Let me go over what Sakurai said.
This isn't "I don't make characters similar in my games". It's "I'm not going to make a whole bunch of characters who pertain to the exact same archetype and fighting style when there are more unique characters I could choose from." In any case, reading what he said literally, he's talking about making
"a ton" of similar characters - not about making
any similar characters.
Furthermore, understand that Lucina is an exception to this because of her origins as a costume. This really does change everything about how her inclusion should be viewed; saying "regardless of the circumstances" when presenting your opinion just doesn't cut it here. It's not black and white.
It's important to note that the context of this is the comparison of Chrom's potential inclusion to Robin's potential inclusion. Robin was chosen for obvious reasons related to his unique moveset potential. This directly supports what he said in the previous quote. Chrom wasn't chosen as a character because he didn't offer more unique qualities than other candidates and he wasn't chosen as an alt costume because Lucina was chosen instead for several reasons. I don't know when it was decided that he would be in Robin's final smash, but deciding to pay homage to what is a large part of Fire Emblem: Awakening by making that happen is also a good enough reason to not include Chrom in another way.
This quote states a few things:
- That Lucina's inclusion began with the idea that she would be a costume
- That he has reasoning for including Lucina as a costume for Marth that is supported by the canon of the game she appears in
- That he decided to give players an alternative playstyle to stick to; in other words, we were given an extra option that we would not have has previously
- She was a "lucky" inclusion, reinforcing once again that she is an exception to the "similar characters" statement because of her unusual circumstances
There is so much in his article that prevents what he's said from being contradictory. You can paint it in black and white terms as you did, but it's just not that simple and reducing it as you did doesn't cut it in my eyes.