Decibel Reductions from Various Hand-Over-Ear Positions

Anyone seen this before:

https://solentacoustics.wordpress.com/2015/11/19/natural-hearing-protection-hands/

It provides simulated calculations of the decibel reductions obtained by various hand-over-the-ear positions.

Some of it slightly wonky (for instance, the cupped hand position looks suboptimal and unrealistic), and they only did 5 runs of each condition, but there are still some pretty interesting findings.

Primarily: you get a 10-30 dB reduction through the finger-in-the-ear technique. This is interesting for two reasons I think:

1. This is a good noise reduction technique!

2. If you can get a 10-30 dB (mostly 20-30 dB) reduction with a finger in the ear across all frequency bands, then why would we do this NRR-7/2 calculation for our ear plugs? I mean, I get that some people put them in badly and not all plugs are as good as others... but if fingers can obtain 20-30 dB reduction, then why would 30 dB plugs get calculated as 30-7/2= 11.5? Seems like this would be far too conservative a value, assuming you have some idea of how to out plugs in.

Thoughts?