Further examination of schematic diagram and ALC ciruit lead me to find few points and questions I couldn't answer myself, so decided to ask Marios SV0CL about.
Here is answer Marios SV0CL send me today :
"" This modification is an easy way to add few miliseconds delay to the ALC action (ALC TIME CONSTANT).
In practice as soon as you start talking to the microphone, power output starts increasing and the ALC has to act and
control this power to the preset level (i.e. 100W PEP)
The IC-7100 has a very "fast" ALC, it acts earlier and voice has no chance to produce much power.
By delaying the ALC action ssb voice has more time to do the job. ""
Marios, asked me also to clearly STATE that WE SHOULD NOT make BOTH modifications together.
This was not clearly stated before, and short modification description did not say anything about.
Althought my radio has both mods and working fine, this could lead to some unexpected behaviour.
I will post any effect of further investigation later.