What it requires. Assignment arithmetic re-derives group totals that a GroupingAndAggregatePricing element should compute.
Why it matters. [reasoned] The aggregation element computes group totals once inside the waterfall; hand-rolled copies diverge when one is edited, and the Price Waterfall's per-element explanation degrades into opaque assignments - discarding the debuggability the platform sells. Two documented carve-outs where manual arithmetic is the only option and is NOT a defect (Trailhead, advanced price management): aggregation elements do not support derived products, and direct rollup to quote or order headers is not supported. Line-level unit arithmetic and those two cases pass this check.
How to fix it. Replace the arithmetic with the aggregation element and let dependent elements read its output.
Source. Salesforce Help: Use Pricing Elements in Pricing Procedures (element vocabulary; mechanism reasoned)
Is this rule worth checking?
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