Program performances after protection

I'm analyzing the performances of a test program after protection with Sentinel LDK Envelope 7.4

Attached you can find the test program. Without protection the execution lasts 30ms. If I protect the .exe with the default parameters the execution lasts 950ms! I try different settings. For example, selecting only the core method and disabling all the protection (see attached image), the execution lasts 500ms. Decompiling the code, LDK Envelope only added

2. \u003442172457.\u00336033679((object) null, MethodBase.GetCurrentMethod(), true);
3.       try
4.       {
5. [...]
7.      }
8.       finally
9.       {
10.         \u003442172457.\u00336033679((object) null, MethodBase.GetCurrentMethod(), false);
11.       }

So, no encryption nor obfuscation decrease a lot the performaces!

The loophole that I found to obfuscate the code and maintain performances is to deselect all methods, create an empty Dummy method and protect only it (otherwise LDK Envelope does nothing) and select String encryption and Obfuscate Symbols in .NET Default Protection Settings.

Am I doing something wrong or this behavior is correct?

Thank you

Best regards

Matteo