According to the AEM guidelines, in-office presence is based on business needs rather than a strict requirement. The "three days per week" guideline is flexible and intended as general guidance. Your manager may request more or fewer days in the office depending on team needs.
Time spent in the office can be minimal, even as little as one hour, and arrival time is flexible unless you are expected to attend a scheduled meeting. Once that obligation is fulfilled, you are free to leave.
If you prefer or need to attend meetings virtually while in the office, for example due to health concerns or other personal reasons, that is also acceptable.
In practice, this means I will go into the office, find an available desk, join the meeting virtually from there, and then leave once it is concluded.