This isn't about "jargon" being used to "be polite". "Jargon" is specialized terminology which may not be understood outside of a group or context. "We took an existing encoder-decoder transformer model from huggingface and slapped a token-level classifier head on it" is lot of jargon. By contrast, everyone understands what "let go" means.
The reason for choosing to say "let go" vs "terminated" isn't to "be polite". More broadly, in this and similar announcements, we see framing, of active vs passive parties, to spin responsibility, agency and involvement. The tone of the whole thing is "because of the broader economic environment, this business outcome was so inevitable and our hands were so forced we will barely acknowledge that it was a decision." And as a stark contrast, they describe all of the things they're giving "impacted" former employees in the active voice: "We'll pay", "We'll accelerate", "We'll cover", "We'll be supporting" etc.
I think they actually seem to be doing a pretty good job supporting the staff they terminated. I just think if they actually want to take responsibility for their actions, both bad and good, they should talk in a way that acknowledges when they're the principal actors.
https://freethoughtblogs.com/singham/2017/06/01/using-the-bu...
https://en.wikipedia.org/wiki/Jargon#Specifics