There was no way around the fact that if he chose to go with this strategy, he would be divulging the truth about his ability to trigger breakthroughs enmasse. Of course, he could try and pin his hopes on the possibility that the Sekigaharans would think it was just a coincidence, but it was way too reckless to put his trust in such a remote possibility.
He needed to accept that if he truly chose to save his friends, he would undoubtedly be sacrificing the secrecy of his abilities.
The consequences were not slight.
Once the world found out what he could do, he would be at a much higher level of danger than ever before.
If not for the fact that he was a Master, and a particularly powerful high-grade Martial Master at that, this sort of thing would have ruined his life. His power was just barely enough to ensure that this sort of secret didn't completely ruin his life.