"Has stopped?" Assuming the translation is accurate, it looks like they have a set of wait-time requirements based on type of vaccine ranging from 24 hours to one year, and "Those who have been vaccinated with the new coronavirus are not allowed to donate blood for the time being." Not sure where you're getting the "This is pointing to the problems of blood clots and spreading this issue to non-vaccinated people through the blood supply and blood transfusions" because I didn't read that anywhere at your link.
Also, you're forbidden from donating blood if you can't understand and respond in Japanese.
"Under the blood donation policy and for safety reasons regarding the person donating blood, we are required to ask you to fill out a mandatory pre-questionnaire in Japanese, and have a certified physician conduct a preliminary medical examination for blood donation in Japanese. Both of these steps will take place on site at any of our blood donation facilities. For this reason, we cannot accept donations from individuals who are unable to understand and respond in Japanese."