When setting custom availability from 11:30 - 2:30, with duration to of an hour. I would hope a recipient could choose options for 11:30, 11:45, 12, 12:15, 12:30 etc. However, because the meeting duration is an hour, the recipient can only choose 11:30, 12:30 and 1:30.
Is there a reason we don't display the in-between times (like noon or 1)?
There are other calendar tools, Calendly and Appointlet, that let you set the start time offsets. So you could display your available times in increments of 30 minutes. And then the available times will update accordingly if meetings are booked.