Avid sent a message offering an smaller HDMI SDI controller. This was being offered as an incentive to purchase some additional equipment. All of the hardware was 3G-SDI which is typical for HDTV class video.
The 12G-CROSS as shown is capable of handling 4K video streams for mastering UHD BD products etc. It also costs less than the hardware Avid was flogging.
4K and 8K video need the higher bandwidth of 12G-SDI which can handle the extremely high bit rates needed.
Avid needs to offer more modern hardware to clients. Nobody wants obsolete hardware considering the unit above with 12G costs less then the obsolete hardware 3G-SDI Avid gear was flogging. The unit was bundled with the $1,299.00 Avid Artist | DNxID.
Mixing units are migrating from Firewire to USB but bandwidth limitations are a nuisance. USB 3.2 is very fast but not yet well supported. Firewire can handle 16 channel mixers easily.
The Windows WAV format file can handle 64K channels which is far more than any mixer can handle. Multitrack editors can use WAV files and digitally mix them to a new track or new WAV file as needed.
Avid is able to work with 16 channels but Audacity is more aimed at 2 track recordings.
Most multitrack digital audio workstation (DAW) packages are overpriced considering the hours needed to develop a package. Firewire audio mixer boards can be leveraged for professional work easily.