It was not really the first time and it started even before BfA. During Amani crisis, Garosh did not send help to Quel'thalas either, so they had to ask Vereesa and Silver Covenant rangers for help. There was a Vol'jin and his shadow hunters involved too, but mostly because Vol'jin took it as his personal matter to deal with Amani/Gurubashi (he also sent Darkspear Emissary to Stormwind to ask for aid), so he did not really acted on behalf of the Horde at the moment.
It's good to see blood elves do not rely on Horde's help and can stand on their own.