A weird question about response to name

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We just redid my DDs ifsp and one of her goals was to improve her response to name. She does respond-- just not 100% of the time. If she's enthralled with something she will ignore but is easily snapped out/redirected if you put your hand on her shoulder in those times.
Last week we had a play date with my friends son who just turned three, so about six months older than dd. he is seemingly nt and very verbal. I notice he does the exact same thing--ignores when you call him if he's really into something. Is this not as atypical for that age as it seems, or is my friends son not as "typical" as I think?