ISO 9000 defines a process as a “set of interrelated or interacting activities which transforms inputs into outputs”.
Ergo, activities are not processes.
I would disagree that 'activities are not processes' is at all implied by that definition. Specifically, Note 3 of that definition in 9000 states:
Note 3 to entry: Two or more interrelated and interacting processes in series can also be referred to as a process.
Thus, sequences of processes can be iteratively grouped into a single higher level chunk which can also be called a process, or conversely, a process can be decomposed into smaller sequential chunks which can each also be called 'processes' as long as the smaller chunks meet the definition of 'process'.
So, there is no specified canonical tier or hierarchical level of "interrelated or interacting activities" to which the term 'process' solely applies.
Clause 4 (and that video seems to agree) seems to want us to focus on a top-level, or higher-level, tier of process organization, but also specifically just on the "value chain" (as used in the ASQ link) processes.
On the other hand, as Big Jim notes, in another clause "special processes" need to be identified, and those are typically going to be identified 'processes' only at a lower hierarchical level of organization; i.e., the identification of that process requires decomposition of a higher-level 'process' into a sequence of smaller chunk processes.
The possible degree of decomposition of a process is also made confusing by the vague definition of 'activity'. In 9000, it is weirdly defined only in the context of projects:
3.3.11
activity
<project management> smallest identified object of work in a project (3.4.2)
However, 'project' in 3.4.2 is defined as "unique
process (3.4.1), consisting of a set of coordinated and controlled activities...", so 'activity' is here rather circularly defined by the definition of 'process'. Moreover, it is a definition only for project management, not for processes generally.
Note also that it says "smallest identif
ied object of work...", not "smallest identif
iable object of work..."
'Activity' is also defined in figure A.6 as
Activity (dictionary word)
doing something
This definition as "doing something" is the epitome of vagueness. But the two definitions also illustrate that 'activity' does not necessarily imply an undecomposable atomic unit - in some cases, an identified activity might rightly also be a 'process', and further, it might also be decomposable into smaller chunks of identified activities and some of those smaller activities might rightly be called 'processes'.