Device differentiation can be done using the IMEI number. I think the question is a vestige of their past blunders and probably some crappy platform.
See, in the past, Orange had those juicy "unlimited" packages that were priced differently for each type of access device (modem/handset/tablet etc). Their general assumption was that there was some practical data consumption ceiling associated with each type device.
Now, their crappy system would provision you to the relevant package but make no subsequent follow-up on what access device you would use thereafter. Additionally, their platform had major frequent hitches in enforcing the data limits. Folks would purchase the 50/= daily bundle available only from a handset, then pop the SIM card into a modem. Voila! Suddenly you got full-speed internet for 24 hours for just 50/=
I guess, as a work-around, they may later have decided to permanently lock the purchased bundles onto some fixed profile - hence the query.
I suppose there are better solutions to managing data bundles that are intelligent enough to spare us those unnecessary questions during provisioning.