The unlimited storage for free was introduced on Google I/O 2015 for all only Android but also for iOS.
Google Photos has just updated its storage policy and starting from 1st June 2021, Google Photos will no longer offer unlimited photos and videos back even you set it in High-quality settings. Whatever media that you have backed up before the mentioned date will not be affected.
So what’s gonna happened after 1st June 2021? The media that backed up through the Google Photos service will count towards your Google Account Storage. The only devices that not affected were Google Pixels 5 and earlier devices.