Wow. Out of curiosity just checked if the other cloud providers have it - both Azure and GCP have this feature already. Azure got it ~ Feb 2020, GCP Feb 20201.
IIRC, we launched interactive serial port access sometime in late 2014. For example, mbrukman answered a SO question on Jan 2, 2015 with connect-to-serial-port [1]. I don’t recall when we gained fancier IAM controls for it, but we’ve had it forever (and I think getting / view only was there at public launch).
[1] https://stackoverflow.com/questions/27734763/how-do-you-acce...
Edit: and really the person who did the most work isn’t mentioned here (that’d be up to them)