Nope it's true
"ICS supports USB Mass Storage (UMS). The Galaxy Nexus does not. This is the same scenario as Honeycomb, as for instance HC supports USB Mass Storage while Xoom does not.
If a given device has a removable SD card it will support USB Mass Storage. If it has only built-in storage (like Xoom and Galaxy Nexus) it will (usually) support only MTP and PTP.
It isn't physically possible to support UMS on devices that don't have a dedicated partition for storage (like a removable SD card, or a separate partition like Nexus S.) This is because UMS is a block-level protocol that gives the host PC direct access to the physical blocks on the storage, so that Android cannot have it mounted at the same time.
With the unified storage model we introduced in Honeycomb, we share your full 32GB (or 16GB or whatever) between app data and media data. That is, no more staring sadly at your 5GB free on Nexus S when your internal app data partition has filled up -- it's all one big happy volume.
However the cost is that Android can no longer ever yield up the storage for the host PC to molest directly over USB. Instead we use MTP. On Windows (which the majority of users use), it has built-in MTP support in Explorer that makes it look exactly like a disk. On Linux and Mac it's sadly not as easy, but I have confidence that we'll see some work to make this better.
On the whole it's a much better experience on the phone."
Think about it this way , instead of having one drive for the OS ( internal memory ) and one drive ( SD Card ) for media , it's going to have only one drive with the OS and a media folder on the same drive and partition instead of the SD Card , you will be able to access this via MTP .
This is not a bad thing at all , before if the device was mounted on a PC you weren't able to access the SD Card , apps installed on the SD Card , music , pics etc. , now you are able to access those files simultaneously with the PC and phone while copying data to the SD card . No need to mount the drive from the drop down menu , just connect and voila . No need to safe unmount .
And if you think it's a downgrade from the previous phones cause you won't be able to see the whole partition , thus the OS folders it's not at all . You weren't able to see the OS folders with the previous phones either cause they were on a different drive that was not mounting to the PC using UMS . All you could see was the SD card which was a media drive now replaced by a media folder .
You are still able to use Root Explorer to see the system folders from your phone if you need to . You can still use ABD to change system files on your phone from Windows .
Think about it this way , instead of having one drive for the OS ( internal memory ) and one drive ( SD Card ) for media , it's going to have only one drive with the OS and a media folder on the same drive and partition instead of the SD Card , you will be able to access this via MTP .
This is not a bad thing at all , before if the device was mounted on a PC you weren't able to access the SD Card , apps installed on the SD Card , music , pics etc. , now you are able to access those files simultaneously with the PC and phone while copying data to the SD card . No need to mount the drive from the drop down menu , just connect and voila . No need to safe unmount .
And if you think it's a downgrade from the previous phones cause you won't be able to see the whole partition , thus the OS folders it's not at all . You weren't able to see the OS folders with the previous phones either cause they were on a different drive that was not mounting to the PC using UMS . All you could see was the SD card which was a media drive now replaced by a media folder .
You are still able to use Root Explorer to see the system folders from your phone if you need to . You can still use ABD to change system files on your phone from Windows .
Guys, chill, the reports are incorrect. USB file transfers will be available once debugging is enabled.
Source: Galaxy Nexus: Enable USB Debugging | Technipages
And gotta love our super awesome Nexus ninja Benson! He dispels myths!
Um....what just happend?
If you mean you noticed something is missing, then we did a little cleaning