Inline binary input: always encoded base-64 ?

I am reading the current Draft version 2.0 of the specification.

In the Abstract:
The requirements specified in the OGC API — Processes Standard build on the OGC Web Processing Service (WPS) 2.0 Standard and specify a processing interface to communicate over a RESTful protocol using JSON encodings.

Then the input is expected to be passed using JSON encoding.

Before Listing 16:
In some cases, for example to pass through firewalls, binary input values need to be encoded in-line in an execute request as a string.

From the above I do infer that there are cases where binary input values don't need to be encoded in-line.
I wonder if it is correct.

From requirement 24:
The service SHALL support binary values encoded as base64-encoded strings.

However it says nothing about possibly supporting alternative encoding for inline binary input.
And I find no way the client can know of alternative accepted encoding when "contentEncoding": "binary" (e.g. Example 4).

Personally I understand there should not be alternatives to encoding base64 the in-line values defined as "type": "string", "contentEncoding": "binary".
Differently the client should be able to know about it.

I expect the specification "type": "string", "contentEncoding": "binary" is applicable only where values are passed by reference,
and it should apply to the referenced resource (e.g. a binary "image/tiff" file pointed by an URL),
but I find it hard to find such an information.
Even more: I would expect the content of a reference URL for a "binary" value passed as reference is not encoded (or SHALL NOT be encoded).

However, strictly reading requirement 26 - B, it would result in expecting the content of a binary value specified as a reference to be encoded base64.
Should be the binary value an exception?

Could you please help?