I think the date is because July 1st is the beginning of a new fiscal year for many companies. I’m not sure why they may have changed terms of service, but my guess is that the companies are required to publish updates at the beginning of the fiscal year.
I didn't notice an uptick in TOS/privacy policy emails myself, but it could be due to today being the last day of June. Companies set their timelines according to fiscal quarters and this is the last day of one.