Good point, although the whole thing about Jaller’s revival was always very muddy. Once the Red Star functionality came into the equation years later, it became even muddier. I am aware of the fact that RS shouldn’t detect beings outside MU, but there have been many different interpretations of the RS limits even by Greg himself. Also the story itself alludes to various options, some of which contradict the MU limitation. I don’t want to go into extremely long discussion about this here, but I can at least try to give few arguments for why Jaller could have been transported to RS:
First of all, one of the few general interpretations floating around, is that the RS can transport anyone inside the MU, but also anyone located within the outline of the GSR, meaning the island of Mata Nui - a product of GSR camouflage system - would be eligible. On the contrary, Reysa was specifically dragged into the Black Water, which lies beyond the edge of the GSR body, placing him outside the RS influence.
Next, Mata Nui island contains several key locations which are in fact elevated parts of the GSR body. One of them is Kini Nui, which includes an entrance to the robot’s insides. Even more interesting is the fact that Kini Nui has its own dedicated teleportation machinery - one able to communicate and transport between other similar key locations of GSR origin, such as the Great Telescope (we learn this in MNOG II). Jaller died in Kini Nui, so it is concievable RS would register him as located in MU. This coincides with the fact that we don’t see Jaller’s body after he died, only the mask. Of course this piece of continuity is retroactive, but it works perfectly. I will also note that Kini Nui is a sensor array of the robot and had a role in sending out summoning signals, so it realy seems the complex machinery and sensors of GSR and RS should be aware that someone is at the site and should be able to communicate this information.
Third and perhaps the most obvious piece of evidence is that RS has built in system specifically designed to detect Matoran outside of MU - the one that transformed Toa Inika. Since the RS can do this, there is no reason why the revival function could not make use of this detection. Perhaps it is connected with the first point I made - the one about the outline of GSR. While the future Inika travelled in toa canisters, they were inside the GSR outline during their whole journey.
I will finish this write up mentioning the theory about Jaller’s revival, which multiple people (including myself) came up with independently. Details may vary, but the core of it is always identical. Takutanuva’s act of transfering his life force temporarily re-energized the broken down components of the RS which prevented revived individuals from returning to the MU, thus teleporting Jaller’s body back (and yes they were inside MU at this point because they were in Mangaia). The mask imprint in this case would serve as a recognition for which body to transport.
The other popular version of this theory also assumes Jaller was revived on RS, but does not include the transportation back. In this verion, a brand new Jaller was created in Mangaia with identical memories personality etc. to the original, while the first Jaller was revived and subsequently trapped on the Red Star. This created a sort of Dekar/Hydraxon situation.
I believe Greg has commented on both versions at some point and the answers he used, did not rule out the possibility of Jaller being teleported to RS after his death. As to the theory as a whole, he did not confirm either version but I recall him saying it made sense.