SiS bar has quite a poor split to compare against.
Do the same comparison with something like a zipvit zv8 and it’s hard to find ‘normal’ food that will digest as easily whilst working hard.
I’d encourage people to check nutritional info on commercial bars before purchasing, as many are not really fit for purpose unless riding at a very low intensity.
To answer the OP, yes, you can certainly make your own, but unless you are training 20hrs a week, you’ll either be forever cooking batches of 4 bars, or won’t be able to eat a bigger batch before it goes bad.