Clarify streaming binary/string usage.

Tighten up the wording a bit to ensure the scope of this
technique is immediately clear.

Author: handrews

src/oas.md

@@ -1665,8 +1665,8 @@ This poses a challenge for streamed media, particularly streams where the client
 
 ###### Binary Streams
 
-The `maxLength` keyword MAY be used to set an expected upper bound on the length of a streaming payload.
-The keyword can be applied to either string data, including encoded binary data, or to unencoded binary data. For unencoded binary, the length is the number of octets.
+The `maxLength` keyword MAY be used to set an expected upper bound on the length of a streaming payload that consists of either string data, including encoded binary data, or to unencoded binary data.
+For unencoded binary, the length is the number of octets.
 For this use case, `maxLength` MAY be implemented outside of regular JSON Schema evaluation as JSON Schema does not directly apply to binary data, and an encoded binary stream may be impractical to store in memory in its entirety.
 
 ###### Streaming Sequential Media Types