Maybe it's just me.
But because the one armed drills and fist drills are a bit restrictive on body movement, I tend to sink easily. So by keeping the legs kicking constantly via the 6-beat kick, I'm able to keep myself afloat and more stable.
Here's how the 6-beat kick in freestyle looks like:
However, I've become accustomed to a quick rhythm when kicking 6-beats. I'm in no way fast, but it's just something I did. So when I attempted to swim slow using 6-beat kicks, it threw me off. It felt very odd since I only did 2-beats (if at all) when swimming freestyle. I had to do several laps and then finally got the groove of it.
I learned that when swimming slow, a 6-beat kick with a bigger amplitude helps. I just need to be aware of body alignment though so as not to fishtail.