ID 484595 - Normal maps High Value can be set above 100% but shows little to no visual difference.

Problem summary
Normal maps High Value can be set above 100% but shows little to no visual difference.
Customer reported version
modo.15.0v3
Customer reported platform
windows10
Steps to reproduce
1) Download and open the attached scene file.
2) Slowly increase the High Value of the normal map beyond 100%. Notice that it makes little to no visual difference.

Expected behaviour
The change to the High Value should be reflected in the Preview render window.
Actual behaviour
Setting the High Value beyond 100% makes little to no visual difference.
Workaround
Unknown.
Reproduced by support
This bug has been reproduced in:
15.0v3 - Windows 10
15.0v1 - Windows 10
14.2v1 - Windows 10
14.1v1 - Windows 10
14.0v1 - Windows 10
13.0v1 - Windows 10
12.2v2 - Windows 10

Earliest version tested
12.2v2 - This issue appears to be in all versions of the product.