You are thinking incorrectly. And apparently reading the leaked release schedule incorrectly as well. It says that the "test dates" for the RAZR ICS build are between 4/19 and 5/17 - meaning it won't even be fully tested until the middle of May. It is NOT releasing during this period.
You will also notice, if you look closely, that the RAZR is currently receiving a bugfix OTA just like we soon will be. The purpose of this is to prepare the device for the ICS OTA, according to Droid-Life's post about said OTA.
I suspect the upcoming bugfix for the Bionic may serve the same purpose. Given the timeline, i'd say we might be in line to receive ICS a couple of weeks after the RAZR at most, assuming there are no showstopper issues with the RAZR OTA.
I am not surprised that the devices are not receiving the update simultaneously, as VZW/Moto seldom push more than one major OTA at a time. The size of the ICS update will be quite a hit on Moto's servers.
By the way, here is the FULL leaked timeline, not just the first page:
Verizon Update Schedule Out; HTC, Motorola Updates Incoming - Other News - droid HIVE - Articles - droidHIVE
For all we know, the Bionic ICS update may show up on the "Week of May 1st" timeline.