"After the end of the recovery interval the device must accept data transfers at any time." simply says that "hardware must be ready (in order to accept data transfer)"
But the "recovery interval" is not defined, leaving the device to decide what its "recovery interval" is and guaranteeing that software will not expect it to be less than 10ms.
USB System Software is expected to provide a “recovery” interval of 10 ms before the device attached to the port is expected to respond to data transfers
