Very well written article - - clear and succinct. And the story approach makes it more engaging. 5 stars.
For discussion (not a criticism):
Regarding the bridge table - - because you have added quantity to the Receipts-Product table, I would think of this table as a fact table. If the purpose of the table was purely for resolving the many-to-many for queries for business information, and not to select quantity, then I would think of that as a bridge table.
If you're going to put quantity in the table, you're more than likely also going to put date, and now the true transactional purpose of the table becomes obvious. And with any transactional table, your non-date keys will probably repeat - so now it is clearly NOT a bridge table.