This is the broadest yet most specific definition of a theme. And yes, ‘any’ means ‘any’.

Themes don’t necessarily have to be intentional, as themes can end up being emergent without the author intending it. Though this shouldn’t be confused with Death of the Author.
Though when people (amateur YouTube critics) talk about themes, they tend to not talk about the emergent ones but the ones that are intentionally placed in a film.

Examples of the type that are intentional would be androids sheep in Blade Runner and “Life, uh, finds a way” in Jurassic Park. Coincidentally, neither of those films explore those specific themes properly. Jurassic Park, in fact, has a different emergent theme: showing the consequences of Zoo mismanagement.

Death Note is probably the pre-eminent example of a work that has an emergent theme: as it sorta, kinda, not really explores the question of what justice is, embodied by Kira or L.
Emergent themes are usually a side-effect of good storytelling – though this is not something that should be relied upon as a guarantee and, further, the presence of an emergent theme isn’t necessarily an indicator of good storytelling.
An emergent theme is also a side-effect of bad storytelling, since a poorly-written plot might have a radically different theme from the intended theme.