The "beta" label signified that we had implemented all the features we thought mandatory for R1. Of course there are new ones in this release (like HiDPI support or the NVMe driver) because we still want to use Haiku on contemporary hardware, so changes still get made. But largely we are more oriented towards stabilization and "usability", i.e. fixing bugs or minor enhancements that get in the way of actually using Haiku.
But it's also the case that we do not get a massive amount of work done every month; probably around or less than a "man-month" between the dozen or two developers.