Something to do with Revision?
I noticed that as well. The original download GOG file was "setup_deus_ex_184.108.40.206.exe" and the updated install file is "setup_deus_ex_goty_1.112fm(revision_1.2.2)_(15442).exe".
Also, the Revision DLC files have also updated. The original download files were "setup_deus_ex_revision_220.127.116.11.exe" and .bin. The new files are "setup_deus_ex_revision_1.112fm(revision_1.2.2)_(15442).exe" and .bin.
I can find no explanation what was changed on GOG. Care to chime in on this GoG?