put a red stone torch somewhere. Use a command to place a shelf directly above it (e.g., setback 1 2 3 oak_shelf). The shelf will show as unpowered, rather than powered. Place a shelf there manually and it will show as powered.
MC-305976
Shelves placed by commands on a block powered by redstone aren't powered
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Can confirm. Shelves placed via
setblockonto a redstone power source do not become powered upon placement like other powerable blocks (e.g. pistons, etc). They become powered only once an adjacent block update corrects it.