I'm not familiar with this particular temporary card, but it's very common for temporary hotel or airline cards to be only usable on that hotel or airline and possibly with other restrictions. For example, when I applied a few months ago for a Chase UA card, upon approval Chase gave me a temporary card number that I could use for UA flights only (and there may have been restrictions on those too); for anything else I had to wait for the real physical card to arrive and be activated.

Now, whether this temporary card can be used only at certain HHonors brands or at all HHonors brands, that's a good question. (To give you the right answer on that, it takes someone who understands the difference between Hilton hotels and Hilton family hotels aka Hilton HHonors program hotels, and that may not the first line CSR, and on a holiday weekend it may not even be some fill-in supervisors.)