I thought that too - then went through all the notices (KBC/BOI) and the notification was always in the month following the ECB change to take effect from 1st of the following month. However as the ECB changed on different dates, it SEEMED the date was closer as I probably noticed the letter dated after a late in the month ECB change more than one where the ECB changed early in the month.
Also, whilst the rate change was announced on June 6th, The date of effect was June 12th
Next rate meeting is July 20th and hopefully another 0.25 and then in sept the "bonus" 0.35% reduction due to realignment of deposit & refinancing rate to a 0.15% spread rather than the 0.5% at current time.