I did the support for the RB26 model (USA version) using a radio supplied by Retevis. Retevis didn't supply me RB626 model (EU version) like they normally do so I didn't do the support for it.
But to investigate I downloaded the latest RB626 programming software from the Retevis website. After installing it, I loaded the RB626 "codeplug" file that was included with the programming software. The Retevis programming software displays the same 32 memory rows as those that are displayed in CHIRP after loading the RB626 image that is available in the CHIRP repository.
According to a table on the HFUnderground's Business Radio page (reproduced below) it appears that the first 16 memory rows are made up from the default frequencies that are included with the Motorola CLS1410 4-channel radio.
Motorola CLS1410 (CLS1110 is the 1-channel version)
Default Channels Frequencies
Channel 1 - 464.5500 MHz 67.0 Hz PL [Frequency 2, Code 1]
Channel 2 - 467.9250 MHz 67.0 Hz PL [Frequency 8, Code 1]
Channel 3 - 467.8500 MHz 67.0 Hz PL [Frequency 5, Code 1]
Channel 4 - 467.8750 MHz 67.0 Hz PL [Frequency 6, Code 1]
These 4 channels are repeated 4 times to populate the first 16 memory rows. Each group of 4 memory rows utilizes a different CTCSS tone.
Memory rows 17-32 appear to be populated with the 16 analog PMR frequencies.
From what I am able to to tell after this quick investigation is that CHIRP is replicating how the programing software that Retevis supplies for the RB626 works. My conclusion, as far as I can tell without a physical radio, is that CHIRP is correct for supporting 32 memory rows for the RB626.