Sorry, but I wasn't able by myself to figure out the reason of introducing chess timer in semifinals. Quick thoughts ....

I guess, the roots lies in:

3. Организаторы при необходимости будут вносить изменения в правила и регламент по ходу турнира.

As far as I know, the golden rule of ethics in games highly recommends do not change the rules during the game / competition / tournament / event.

Despite this, the statement 3 is absolutely logical and necessary if used only in emergencies by serving as a legit tool to control / fix / eliminate crucial defects / game bugs unknown at the time when the rules were written.
*Seems like it doesn't give the freedom to add / change / improve / simplify existing rules for any other reason.

Probably a change of rules during a event may happen:
- as result of unanimous request from participants
- as result of recommendation, if participants unanimously adopted it

I haven't noticed a mass complaints on regular timer or mass request for chess timer among novices.

Furthermore, couple facts:
1. all participants agreed and pledged to play in this tournament with regular timer ( obviously, by enrolling in tourney )
2. some of them can also play with chess timer (obviously, by participating in chess timer survey)

For sure somewhere I am wrong or I missed something, but still don't have a clue, what was the necessity of such change?

Thx in advance for clarifying the decision.