[gentoo-user] Problem understanding "eix"

[Dr Rainer Woitok]

Greetings,

after several days of manpage reading, head scratching,  and testing the
reactions of "eix" to various input  I'm giving up  and ask the combined
wisdom of the Gentoo list.

Here's the version of "eix" I'm using, my test script, and its output:

   $ eix --version
   0.33.9
   $ cat test-script
   #! /bin/sh
   export EIX_LIMIT=0 OVERLAYS_LIST=false PRINT_COUNT_ALWAYS=never
   export FMT="<category>/<name>\t<version>\t{isstable}1{else}0{} {!isunstable}1{else}0{}\n"
   echo in:
   eix --format '<installedversions:FMT>' \
       --category-name --regex 'app-crypt/tpm2-tss$|acct-group/input'
   echo av:
   eix --format '<availableversions:FMT>' \
       --category-name --regex 'app-crypt/tpm2-tss$|acct-group/input'
   $ ./test-script
   in:
   acct-group/input	0	0 1
   app-crypt/tpm2-tss	2.3.3	0 1
   av:
   acct-group/input	0	1 1
   app-crypt/tpm2-tss	2.2.3-r2	1 0
   app-crypt/tpm2-tss	2.3.3	1 0
   $

And finally here are my questions:

1. Why do the  package properties  "isstable"  and  "!isunstable" differ
   from each other in four out of five output lines?

2. Why does the package property "isstable" return different values, de-
   pending on whether it is called  via the "<installedversions:...>" or
   "<availableversions:...>" property?

3. How can I reliably retrieve the correct information whether a package
   is "stable" or "testing"  for both properties,  "<installedversions>"
   and "<availableversions>"?

Any information appreciated.

Sincerely,
  Rainer