Implementation Requirements: in spec considered to be conformant spec, and it should not have tight coupled to some internal JDK implementation
references.
There are instances which are mentioned as Implementation Requirements but their behavior is coupled with the non exposed JDK libraries.

In RandomGenerator :
default float nextFloat​(float bound)
Implementation Requirements:
The default implementation simply calls checkBound(bound) and then boundedNextFloat(this, bound).

nextFloat​(float origin, float bound)
Implementation Requirements:
The default implementation simply calls checkBound(bound) and then boundedNextFloat(this, bound).


default int nextInt​(int bound)
Implementation Requirements:
The default implementation simply calls checkBound(bound) and then boundedNextInt(this, bound).

nextInt​(int origin, int bound)
Implementation Requirements:
The default implementation simply calls checkBound(bound) and then boundedNextInt(this, bound).

nextLong​(long bound)
Implementation Requirements:
The default implementation simply calls checkBound(bound) and then boundedNextLong(this, bound).

nextLong​(long origin, long bound)
Implementation Requirements:
The default implementation simply calls checkBound(bound) and then boundedNextLong(this, bound).

RandomGeneratorFactory::all()
Returns a non-empty stream of available RandomGeneratorFactory(s). RandomGenerators that are marked as deprecated or are not properly configured are not included in the result.
Implementation Requirements:
Availability is determined by RandomGeneratorFactory using the service provider API to locate implementations of the RandomGenerator interface.

Here - not property configured is confusing , and configuration coupled to internal JDK classes.

As I understand these looks to be Implementation Notes.