The sentence you quoted refers to the period between first and second dose. My understanding is that "if you get exposed to the Delta variant on the day before the second dose, you won't have neutralizing antibodies".
It does not make a statement about what happens after the second dose.
Agreed, but it is suggestive that this is within the realm of possibilities, no? Otherwise, something interesting would have to be happening where after the first shot you lose delta ~immunity in eight weeks, but after the second you ~do not?
Possibilities sure, but IMO that doesn't translate to "likely". Other vaccines also give you only minimal or short protection after the first dose with long-lasting protection after the second (or third) one.
It does not make a statement about what happens after the second dose.