Dave Platt wrote:
You can, however, program two or more OTP generators with the same
shared secret, if you choose. For example, if you own a smartphone
and a tablet, you can sign up with a service that offers one-time-code
access, get your secret (some services deliver it as a scannable
barcode or QR code), and load the secret into an OTP-generating app on
both devices. These devices will then generate the same code
sequences and you can use either to authenticate.

That works, but only when the device has accurate time synchronization
by another method. E.g. NTP.
If not, the times on the two devices will differ, and the algorithm
in the server that tracks the time offset will fail.