Since code switching can occur on a
single-word level as well in longer utterances, length
of utterance does not offer a clear-cut distinction.
Phonological adaptation also fails to be foolproof.
For example, if a bilingual speaker has transferred
the phonological system of L1 to L2 while acquiring
L2 (in other words the speaker has an accent), it will
be difficult to evaluate whether word X from L2 has
been borrowed into an L1 sentence or if the speaker
has code switched into L2. Most researchers ac-
knowledge the shortcoming of using morphological
adaptation as a guideline in cases where the switch
may be only one word such as an adverb or an unin-
flected free morpheme.
Encyclopedia of Language and Linguistics (ELL2)
S. Mahootian, очень богатая статья

Но подчеркиваю, что согласен, просто сам перепостил это видео прежде, чем задумываться над ним.
И извините за лавину комментов :)