I realise that there is a lot to cover when creating an article such as this, and part of doing a good job is knowing what to leave in and what to exclude. Well done for giving this a go.
But I would suggest that your Multicast / row number example is not a good one, because no one would ever design a package like that in the real world. We don't want newcomers learning bad practices from day 1.
Instead, why not simply
1) Excel source to
2) Rowcount to
3) SQL Server destination
In your example, the data does not 'go anywhere', and I can imagine this being puzzling to those new to SSIS.
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