XT1039 cannot get 5.1 OTA if I am root (but still on Stock 4.4.4)?

I own a XT1039 (moto g 4g 1st gen) and currently have unlocked bootloader and rooted.
Yet, I am on stock rom 4.4.4 and 21.11.56.peregrine_retgb.retgball.en.GB

I just contacted motorola on chat and they informed me that:
1) there is only OTA for updating to 5.1 (no way to download or load by pc Motorola Device Manager)
2) cannot guarantee that I will get a notification for the update because I m root.

I see here,
that my device should already have the update

Any help, please?..

PS. I do apologize if there is duplicate for my post, I could not locate an answer...