Sony - Xperia XA2 - pioneer - Documentation Suggestions

Hi,
after having run the /e/OS Pioneer for quite a while (i.e., 1.8.1-20230207257879-pioneer) which is Android 10, dated February 7th, 2023, on an xperia xa2 today I decided to finally do a step-by-step upgrade to Android 13.
But first I would like to share some observations in comparison to my previous post on this topic:

  • it seems that the device-id has changed, i.e.
$ fastboot devices
CQ3001GG7C	 fastboot
  • the nature of the slots seems to have changed (i.e., I get a reply only every second call)
$ fastboot getvar current-slot
getvar:current-slot                                FAILED (remote: 'GetVar Variable Not found')
Finished. Total time: 0.001s
$ fastboot getvar current-slot
current-slot: a
Finished. Total time: 0.001s
...
  • the slot-variable does not seem to be supported any more
$ fastboot --set-active=b
fastboot: error: Device does not support slots

Versions:

$ fastboot --version
fastboot version 35.0.1-11580240
$ adb --version
Android Debug Bridge version 1.0.41
Version 35.0.1-11580240

Coming to my question: For the upgrade I decided to follow the step-by-step-, version-to-version approach. However, I just have a problem with the first upgrade step, from Android 10 to 11:
Following the procedure as described here, i.e., to sideload the most recent version of Android R in the
download section.
After a successful sideload

$ adb sideload e-1.8.1-r-20230206257804-dev-pioneer.zip 
serving: 'e-1.8.1-r-20230206257804-dev-pioneer.zip'  (~47%)    adb: failed to read command: Success

a message on the smartphone appears, that the image that I try to install (the most recent from Android 10, e-1.8.1-r-20230206257804-dev-pioneer.zip)
is older than that, which is currently installed (1.8.1-20230207257879-pioneer) and that this is prohibited by the installer.
Did anyone face the same problem and found a solution for that?