I chose this company over other options because they said they are ok with remote working. I explicitly asked them if I can work completely from home and they said yes, some of their developers are always travelling and working remotely.

However, after I joined, the boss of my boss told him that he wants people to come to the office at least once every 2 weeks. I feel slowly they are going to make it more frequent.

Is this ok? Should I tell them that if they said 100% remote is ok in job posting, they should adhere to that? Or should I keep silent?

I don't want to lose the job. I spent 3 months searching for a job. I had 3 amazing offers and I turned down other offers just because this one offered 100% remote.