Often times the "fluff" has no trouble carrying through between editions but the crunchy parts often change. The Clawdite is an example of that.
It seems that both the fluff and mechanics did change even though some things were carried over (Clawdite history and +10 to disguise checks). Partially that's because the mechanics changed partially because maybe the Shi'ido are no longer a playable race.
Because of the flexible nature of SAGA's classes I imagine that those things you see in the RCR's Changeling PrC would simply be feat in SAGA and/or a should have been in a talent tree that never materialized.
Looking at that list of things you mention the Changleling class doing I can see Natural Weapons as a combination of the Martial Arts feats which also benefits from that size boosting feat. The CON damage is already removed. Shapechanging time would probably have been covered by something else but altering your appearance in a round without a penalty for being rushed already covers that for the most part.
I think that without the combat applications (natural weapons, armor, DR) that the need to be faster than a full round isn't really needed, I wasn't really interested in those any way, but the UAA version seems to focus on those combat improvements. SWSE does have two feats that seem to have the goal of giving a Clawdite more combat ability through shifting: Metamorph and Hideous Visage, but they don't match mechanically what the UAA species/PrC does and I think aren't worth taking even for a martial artist.
The first level of the UAA PrC gives something similar to the SWSE Impersonate feat.
And it seems the Con damage and removal of the Con damage on shifting in the PrC have basically both been removed with the PrC no longer existing.
As far as the fluff, the SWSE version is much less detailed on what the shapeshifting allows a Clawdite to do.
"they can assume the appearance of a similarly size species, even masking their equipment when it's held close to their bodies"
is about the only relevant fluff in SWSE.
My conclusion is that the changes are big enough that I can't assume that fluff from UAA automatically applies in SWSE and the description in wookipedia seems to be largely based on UAA. The description in SWSE is possibly much more vague on purpose, leaving it up to the GM to decide the mechanical limits and fluff much more. The fluff text in SWSE is actually longer than the one in UAA, but focusses almost exclusively on a much more detailed history of the Clawdites. Someone must have decided on a rewrite on purpose. The text from UAA is at best an indication of what an earlier writer thought, but given that it was rewritten, someone must have had different ideas for SWSE.