There is a concern that a malicious hacker, if they gain access to your device, could re-purpose speakers to act as a crude microphone, thus circumvent microphone hardware kill-switch found on Librem Laptops and Librem Phone.
This is not concern with Librem devices.
In Librem Laptops: the speakers are connected to an amplifier since the codec itself can not drive a speaker. The amp will for sure not work backwards as an input amplifier, quite the contrary.
In Librem Phone: The codec in the phone uses DACs to drive the speakers, and they can not be re-tasked as audio inputs.