Yes, it's possible. I'm using the EF100-400 L for macro photography, indeed it's not an extreme macro but the short focal distance of this lens and the 1.6x crop factor of the R7 allows you to take detailed pictures of insects or flowers.
Some great shots there. To be strictly correct, you are taking close-up shots. Macro is defined as where the image on the processor is 1:1 with the actual size of the subject. These days the term has been used very loosely by lens manufacturers to push their products.