-
Rendered over or not it's poor work.
Id put money on the builders doing the same with other things if it's not pointed out and addressed tbh.
If you've paid your architect to manage the build , id explicitly ask them to discuss with the builder and reach a resolution. They should be well versed in such discussion.
You'll have to live with whatever the builders do , so make sure they do it right . It may be just a single corner cut and there may not be others, but nip it in the bud all the same
I've emailed the architect and sent photos, asking him what he thinks and when he'll be on site to take a look.