That story was a comic bit of filler than Lee probably didn't spend too much time fine-tuning. It also has him giving two different versions of the beginning of Reed and Sue's relationship in two consecutive panels.
The part you're referring to is clumsily done, but it's more than just "Lincoln had a mom." It's Reed responding to a fan letter-very angrily, it might be worth pointing out-that essentially said "Why do you have Sue on the team, her powers are useless." Reed's answer was in two stages. 1) Your premise is wrong. You don't need powers to be useful. 2) Your premise, even if it were right, wouldn't apply here because Sue has been a valuable active member of the time. One of the examples given was the same one that Byrne used, her saving them when they met Dr. Doom.