Well, this has to do with all our Windows 10 betas. In the beginning when Microsoft started to push out these ESD files I converted them and added both the ESD and ISO on the FTP. The conversion was cumbersome at first and the conversion would help members to use the beta "out of the box" without any fuss with the conversion. We also didn't know if this ESD distribution method was a temporary solution or a more permanent one, but as it seems it became a more permanent way for Microsoft to distribute new builds, and the conversion has become far easier now with the ESD decrypter tool and the variant gus33000 has made for us (the lack of official name for it made me dub it the "GUSTools"
). Therefore I don't see any reason to keep any of the converted ISOs on the FTP anymore. It's easy for each member to grab the ESD and converter tool and convert the ESD themselves, this way we save some precious space on the FTP and the releases become smaller as a result. Also, the ISOs were not originals and therefore against our long term goal to have as many original and unmodified/non-custom releases as possible.But this deletion of the ISOs has the "unfortunate" effect of decreasing our archive size. This is of course understandable but in the long run it doesn't matter. Our aim isn't to chase the highest archive size number, but to have the most correct releases for you members. Over time the archive size will again increase in size and eventually go beyond the previous size.
