Yup, we've also noticed that. Webhooks wont be sent when the status is changed through bulk updates. It does fire if the merchant changes it at the product level. Can't recall whether that was the case for all stores or some of them. Hope @Shopify team can shed some light on this.
I am Charly, Lead Software Engineer of the Algolia Shopify Integration.
We face the same issue for all of our customers, it's so frequent that it's even documented on our FAQ: https://www.algolia.com/doc/integration/shopify/troubleshooting/frequent-issues/#products-dont-get-u...
We would love to see a fix on that issue too!