That's only for the telemetry that happens during the install process (if I've read the link correctly). Seems quite reasonable as long as we accept them sending telemetry during install. ("A single telemetry entry is also sent by the .NET SDK installer when a successful installation happens")
For telemetry during actual use, you can set that flag any time, and a message is shown on first use to inform you about it.
For telemetry during actual use, you can set that flag any time, and a message is shown on first use to inform you about it.
So seems relatively reasonable to me.