Yes things were moving fast even then.
This was late in the game.
The Altair when first available had 4 cards for IO, the SIO-A (single
serial), 2SIO (2 6850 serial ports), PIO(parallel) and the infamous ACR.
The Digital Group developed boards that were the equivalent.
At the time of the demo the ACR was available with
usable software. Why
they chose TTY loading to this date is speculation.
Keep in mind this was a group of sales types and maybe they
didn't have everything with them.
What Sudding did do was to make the 300baud (30CPS) ACR and the 300baud
(also 30cps) Kansas City standard look slow by pushing to 1500baud
so that loading at 150cps was doable. However the Sudding standard
never caught on as it was not tolerent of some problems (tape speed).
The Tarbell standard would give a higher data rate and was self clocking.
So went the audio casette hardware wars. When it was reaching it's peak
most of us were looking at either real tape (saturation with block
replaceability), disks or disk like systems.
Yes there was no question that disks were the way to go.
Allison