I just don't like the way they conveniently omit that the version of AmigaOS they replicate is 25 years obsolete and modern "Amiga OS Conform Software" is actually not supported, it's misleading.
Noone wrote "supported", the word used is "runs", which is true. And "modern" Amiga software? Let us not kid ourselves, nothing "modern" going on here. What AROS does is replicate the APIs, not the the software that the OS shipped with - all APIs are in place for also Reaction to run, it just happens that the owners of Reaction do not wish to see it on AROS - which is totally fine, because Reaction has _very little_ to offer over what is already present. And if you _REALLY_ desperately need Reaction on AROS, you can have it - you have shown up through the years that you have no problem ignoring copyrights and distribution licenses, so you should have no trouble using unpacking a reaction.lha archive on your AROS/68k system partition.
Anyways - AROS moves on with or without you, you can mix and match with "real" AmigaOS all you like.