According to Mike:

There are other properties though, where they are not lists of whitespace
separated values, it's just one value. Example: escapeBlockStart. This
could be something like '[BEGIN]', or XML's famous '<![CDATA[' . If it
wanted to have whitespace between the brackets and the word you can't do
'[ BEGIN ]' according to the rules. You have to do '[%SP;BEGIN%SP;]'. I
believe if you write '[ BEGIN ]' it should SDE because an individual
string literal has non-entity whitespaces.

I created a test that represents this and it parses with no error.

See test whitespace_01 in the following files:

daffodil-test/src/test/resources/daffodil/section06/entities/Entities.tdml
daffodil-test/src/test/scala-debug/daffodil/section06/entities/TestEntities_01.scala
daffodil-test/src/test/scala/daffodil/section06/entities/TestEntities.scala