[Avid-L2] Delivery Spec Curiosity?

I've successfully delivered the files but I'm curious about one thing.  The delivery spec requested audio as AAC 16bit.  I exported from Avid MC 2018.12.15 and set data rate etc...  I saw no option of 16 or 24 with AAC selected.  Is AAC always 16 bit?  I'm going to google around but thought I'd throw it out to the collective and perhaps somebody else will benefit from the answers.

Here is the delivery spec:

Video File Specs

                File Format: MPEG-4 (.mp4)

                Total Stream BitRate: 33 Mbps Video Stream

                Codec: AVC (H.264)

                Frame Size 16/9: 1920x1080

                Frame Rate: 29.97 fps

                Pixel Aspect Ratio 1:1 (square pixels)

                Video Standard: NTSC

                Scan Type: Progressive

                Video Stream BitRate: 33 Mbps  

                Video Stream BitRate Mode: VBR

 

                Audio Stream Codec: AAC

                Audio Stream BitRate: 320 Kbps

                Audio Stream BitRate Mode: CBR

                Number of Audio Channels: 2 (Stereo)

                Audio Channel's Positions: L, R

                Sampling Rate: 48khz

                Bit Depth: 16 bits

John Moore Barking Trout Productions Studio City, CA bigfish@pacbell.net