I have a previous generation Bosch 500 series dishwasher. For my use case I get the best results with the heavy cycle. However I found that adding loose detergent in there for the "prewash" resulted in soapy residue being left on the dishes if used in conjunction with the heavy cycle (but not with the normal and auto cycles).

Alec's dishwasher videos are based on some rather primitive dishwashers. For instance he talks about his test unit not flushing out the spray arms, but Bosch/Siemens filters the water going to the spray arms so it wouldn't recirculate dirty water anyways. Same deal with the prewash. Bosch uses a turbidity sensor to determine how many "prewash" cycles to run and when to reuse the water, something his test unit very clearly does not.