Is "release" countable when used to mean "to let go" or "to make available"?

Question

Is "release" a count noun or mass noun in the meaning of "let someone or something out of a place"? I see conflicting information from different dictionaries, even within the same dictionary.

MacMillan defines it as uncountable:

[UNCOUNTABLE]
The release of Nelson Mandela was watched by millions of people on TV.
We’re doing all we can to prevent the release of toxic waste into the oceans.
the release of secret government information

But the same usage is defined in Cambridge Dictionary as countable or singular. I saw this line on the Internet, which seems to suggest it is countable:

A judicial mandate to a prison official ordering a prisoner be brought to court in order to determine imprisonment or a release from legal custody. (source)

But there are also other examples that suggest otherwise. Is "release" countable in this definition? What about in this following sentence? Can it be pluralized?

We knew that the game’s release was imminent.

Answer 1

As countable: - There were 10 political prisoner releases last year. [possible though awkward]

• There were ten dam (water) releases on the river last week.

• There were 50 album releases at that company.

As uncountable: - Release of prisoners can only be negotiated by lawyers.

It could be argued that the Nelson Mandela release example is used "uncountably".

If a person is released from prison twice, you wouldn't generally say releases. You would say:

He was released from prison twice. That's the kind of logic they are using to say release is uncountable in this particular context.