We reassess recent conclusions, drawn from observed on-line differences, that (mature) native and (developing) nonnative sentence processing are "fundamentally different," such that only nonnative processing is generally characterized by lack of morphosyntactic detail but over-reliance on lexis, context, world knowledge and default processing strategies. We discuss four potential causes for observed native vs. nonnative on-line differences, none of which implicate differences in the nature of on-line sentence processing in the two cases: (1) native vs. nonnative prosodies imposed on written stimuli; (2) native "overlearned" vs. nonnative "underlearned" lexical-access routines; (3) the structure of the native vs. nonnative lexicon, causing distinct presuppositions induced by native vs. nonnative heteromorphy of semantic fields associated with specific lexical items. Suggesting that (1)-(3) lead to slower processing on the part of nonnatives, we argue that (4) comparisons on planned segments may in fact reflect different "moments" in the parsing process of natives vs. nonnatives. We reconsider data from Marinis, Roberts, Felser and Clahsen (2005) in this light. In sum, we argue that the mere observation of (mature) native vs. (developing) nonnative difference does not imply "fundamental difference"—neither for knowledge nor for processing.