If we accept that the Inmarsat arcs and the radar trace are correct then we have a timing anomaly. If MH370 maintained its last known course - the radar track - then we have a problem because it would cover only about 140NM between two ping arcs which are timed at 1 hour and 12 minutes apart. It is speculated therefore that the aircraft took a large and unexplained northerly diversion (the hook referred to in the Australian report) in order to maintain both a plausible airspeed and the timings of the satellite pings. There is as yet, no reasonable explanation of why this should have happened.
There is a reasonable explanation which does not require a northward excursion. The portion of the 18:29 (The BTO data was obtained at 18:29, not 18:25) ping ring plots as nearly north - south (NNW-SSE) at the point it is likely to have intersected the flight path of MH-370. The exact point where the flight path intersected the ping ring was at about 6°32'34.04"N 96°42'17.66"E. this is about 20nm east of where the Malaysians have vaguely given it's position at 18:22. I accept the Inmarsat BTO data as accurate and thus ignore the Malaysian position estimate at 18:22.
As you say, the 19:40 ping ring does lie only about 140nm from the 18:29 ping ring - and it is probable that 9M-MRO did cross the 19:40 ring or pass very close to it about 18 minutes after reaching the 18:29 ping ring.
However at that time (about 18:47) there were no satellite communications in progress, so there was never any BTO data collected to reflect that time and place. Thus the 140 nm distance between the two ping rings is meaningless as far as 9M_MRO's flight path is concerned.
What happened at about 18:47 was that 9M-MRO turned south - and when the 19:41 Inmarsat transaction took place and logged the BTO data, 9M-MRO was at about 2°38'57.58"N 94°42'33.49"E (plotted for a 376kt speed) or about 1° 3'43.56"N 94°42'30.43"E if the plane was flying at 470kts.
The 19:40 ping ring also traces an almost north - south path at this longitude so 9M-MRO was on or near that ring for over an hour on its journey south but it was only at 19:41 that the BTO data was collected.