This is probably a reference to GPLv3's anti-"tivoization" terms. That is, the GPLv3 requires that recipients of embedded GPLv3 software must be able to deploy modified versions of the software in the device, if the device supports that capability:
If you convey an object code work under this section in, or with, or specifically for use in, a User Product... the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).
“Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source. The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.
For example, this disallows cases where a device will only run software updates that have been signed by an authoritative key held by the device manufacturer. Instead, if you have a device that comes with GPLv3 software (or, more generally, if you have GPLv3 software intended for use in a particular device), the GPLv3 requires the distributor to offer you the necessary keys and instructions to update that GPLv3 software inside the device.
To put it another way, if the device can receive software updates, the user must have the ability to install any modified version of the GPLv3 software, whether that modified version was published by you, or directly edited by the user, or created by any third party. It must not ever be the case that the user has in hand a modified version of the GPLv3 software for your device but is forbidden from installing it on the device. You cannot maintain the exclusive ability to install software on the device by means of secret keys or secret installation protocols. You are welcome to charge money for a copy of updated software for your device, though if the software update is under the GPL or LGPL, you must give the user a copy of the source code under that same license so they can share it with others.
Technically, there is no requirement the device must allow the user to extract already-loaded software out of the device, but this doesn't really matter. You are always required to give the user human-accessible, buildable source code when you give the user GPL-licensed binaries, whether by download, on media, or embedded in a device. The device doesn't need to give the user access to its source code, because you already gave the user source code alongside the device or downloaded software update.
Since the LGPLv3 is an set of additional permissions on top of the GPLv3 (which do not interfere directly with these requirements), this applies equally to the LGPLv3. However, as you might expect from the LGPL's weaker copyleft, you only need to supply the instruction to update the LGPL library, not the entire software on the device. Exactly how to provide an update mechanism that limited to updating to a single library seems like a strange technical problem, but it is legally allowed under the LGPLv3's more narrow scope of this requirement.