Solar steamed soil shows much faster growth in the first month after transplanting lettuce.

I was filling a planter with solar cooked soil but ran out half way,   so I filled the rest with uncooked soil.  I transplanted lettuce into the lot.  I expected a slightly cleaner crop in the solar cooked soil (no weeds) but it was also a deeper green and now after about 28 days, it is growing considerably faster too.   I can think of lots of reasons.  But is what it is,  a definite improvement in the first month.  Anyone else want to try it?   Here is a short video showing the difference.