I have the same experience as above:
No further updates here at present - any update will be shared the moment it arises, for sure. Thanks for the patience all whilst we are resolving this. Please bear with us!
This is happening to us as well. But only for products that have one variant. If you update the variant information (e.g., price field) you'll get no webhook. If the product has at least 2 variants you'll get the hook to fire. We informed Shopify of this over two weeks ago. They have confirmed that there is a bug on their end and that their engineers are looking into it. We are waiting on an update on this still.
This is an accepted solution.
Shopify's API Support here with an update. A fix to resolve this has now shipped to production and this would be resolved.
On the product page, the product/update webhook is firing when editing the price. Additionally, editing the quantity on the product page had been reported as not firing the product/update hook - this is also resolved.
Appreciate everyone's patience whilst we've been working on this! Hope this helps - thanks!