The difference between Bishop Williamson consecrating bishops and the SSPX consecrating bishops is that the SSPX, in 1988 and now went thru the proper channels for papal approval even though they knew both time they would not get it.
Riiight. So SSPX get an "A for effort" and the old "participation trophy". Doesn't matter that the end result only proved Bishop Wiiliamson correct.
So, the perfect analogy here is ... SSPX says "we must make an effort to run 25 miles in 30 seconds." Williamson says, "I'm not going to bother, since it's an exercise in futility, plus you might get a heart attack trying."
But even though the end result is the same, there is a formal difference, namely where the SSPX are so weak regading their profession of the Traditional faith that they believe it to be COMPATIBLE with the Novus Ordo Religion, and capable of existing side by side with it. +Willamson said (correctly) that it's not.
This is quite similar to the debate between "Bishop" Athanasius Schneider and Archbishop Vigano, where the former thinks that Vatican I can be fixed, and that a few accidental course corrections can restore the Church, whereas +Vigano held that the two are radically incompatible, and that there can be no (Hegelian) synthesis between the two, and the Conciliar Religion, with all its pomps, and all its works, i.e. Vatican II, the NOM, the new "saints", the new moral law, 60 years of Modernist pseudo-Magisterium, it needs to all be disposed of tidily in the waste bin before there's any hope of a restoration ... since the two are radically incompatible.