The built-in IRs for the Convolution Reverb come free of charge for anyone who is using the plugin, these are owned by Audiokinetic and thus distributed for free with the plugin regardless of the license plan so you are free to use them.
The platinum plan does include all Audiokinetic plugins, but no 3rd party plugins, so if you are looking to use the BOOM Library or AudioEase IR packs/products these would be license on top of the Platinum license, these are not the same as the free included IRs that come with the Audiokinetic Convolution Reverb. The 3rd party IR packs are used with the convolution reverb but are extra charge regardless of the license plan.
Hope this clears it up,
For any other licensing questions, feel free to use the "contact my sales representative button" on the registered project page.
Cheers,
-M