Currently there is no support for generating armv7 vm images in the release artifacts. In fact in terms of release artifacts and architecture there is no good reason to have a vm release artifact for armv7 as those are mostly used in SOCs or embedded boards. However if you consider that developers actually do need an easy way to test armv7 with a vm running this is really important. As me and @lwhsu are working on pre-commit ci for developers this can be really helpful for the end developers.
I have already done the work on pre-commit CI at https://reviews.freebsd.org/D43786 which supports building images utilizing the release scripts itself. So once we can merge this we will add more test facilities when we can see the real benefits.