Slitherine

for your info:

background:
I use enemy strongpoints to farm "dependable support" award progress. Enemy strongpoint, my Tank with my AT behind. If AI strongpoint is too scared to attack my unit, I split the AT behind.

finding:
After strongpoint attack f.e.: AT part a has 11 dependable support progress (hover over medal) and AT part b has 12 dependable support progress. If I re-combine the units and move the 11 dependable support unit on the 12 ... the combined unit has 11. So I have to move the 12 dependable support unit part on the one with 11, so the additional progress isnt lost.

tl;dr If you combine two splitted unit parts with different award progress, always move with the part with higher progress on the other one

Next time the maps need strongpoints with extra stats and 99 strength then I guess.

Jokes aside, I rarely used this method as there was usually something else to do on most maps, or specific run rules did not allow it for me because of core composition. I usually trained bombers on these if there were no other reasonable targets. Sometimes fighters even, after all, each attack is still 1 experience at the very list even with 0 damage. Still, it is one of those little tricks that can be done to quicken awards, like:

1. Overrunning mines with fresh tanks upgraded to a PT-34 in Grand Campaign to quicken Steamroller (or just sniping 1 strength mines with tanks when possible). This has limited usability as it requires captured stock given later in the campaign, at which point most tanks should already have it. Can get that steamroller much quicker on a fresh unit if ever needed I guess.
2. Getting Double Attack on reasonably armored artillery and purposefully hitting other artillery while in Counter Battery fire range for easy Survivor (suppress the artillery a bit with strategic bombers for reduced damage if no good armored options are available).
3. Those few missions like "Bombing Stalingrad" where specific AA gun formations allow to farm maximum Survivor in one attack.

What is useful the most I'd say is the note about the game rounds up or down on the numbers for the awards. I never bothered to check, but no I will whenever combining units since especially support fire awards can take some time to gather. I never gave it some thought how splitting/combining affects it, so thanks for the input. I guess Steamroller Overrun count would work the same way on split units, but splitting tanks for overruns wastes the kills, so I doubt anyone would actively do that. The infantry Close Defense award also, although that might not really be something that would come up often.