🔑 The level found is typed, and so is the chain below it. A consumer that walks on from the level it asked for reads ->weight at every depth, never ['weight'] one step down : the walk hands back the same shape Reflection::hydrate() builds, not a typed head sitting over raw rows.

The chain is read one level at a time, valueReference after valueReference, until the type is met or the chain stops.

🔑 The tree is a parameter, not a property. The walk belongs to whoever holds a chain, and a chain is not always reachable from the product that defined it : it is built at import time, copied onto the offers, and it is that copy which is stored — so a product read back from a base has none, while the offer beside it does. Left private on the product, the walk had to be written a second time by anyone holding the offer's tree, and a walk written by hand rebuilds the levels as plain QuantitativeValue : that class declares neither weight nor volume, and a class discards the keys it does not declare. Both would leave without an error and without a trace. Exposing the walk is what makes that loss impossible rather than repairable.

⚠️ Schema.org lets valueReference hold things that are not quantities at all — a bare code, an enumeration. Anything that is neither an array nor a QuantitativeValue ends the walk instead of being read as a level.

Example:

$parcel = findPhysicalQuantityByType( UnitOfSaleType::PARCEL , $offer->eligibleQuantity ) ;

$parcel?->weight ; // 245.1456