[pcc]

If you copy or distribute the derivate work in either object code or executable form, you are obliged to make the source available.

Arguably anyone who has a phone, has had a copy in executable form distributed to them, and can ask for the source.

[calloc]

He was talking about Google's private fork of Linux for their servers to run Google search.

[pcc]

He was talking about companies in general tweaking linux for their particular uses.

Indeed, if you focus on the preceding bit about Google's in-house linux for their own servers, then there would be no distribution and arguably GPL2 could not force those modifications to be made public.

But I would imagine that he's probably quite versed in GPL2 and knows this -- so since he brought it up specifically, it suggests he was probably thinking at that point more about cases where distribution does happen (e.g. Android, embedded etc).

Perhaps he considers it a 'significant change' primarily if there's some sort of distribution ;)