If one uses command to create a bow with power level above 255, for example, {lvl:15000s,id:"power"}, and then uses this bow with "Power enchantment.level.15000" to fire an arrow, the "damage" NBT of the arrow would be 130.0d(corresponding to power level 255) but not (2.5 + 15000 * 0.5) = 7502.5d (corresponding to power level 15000).
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Is this MC-10755 ?

@robbage
No, this works fine before Minecraft 1.16.

Yes, it is MC-10755. That level of Power is not supported and never has been, just because it worked in the past does not guarantee support.
Helló!
(2.5 + 15000 * 0.5) = 7502.5d (corresponds to the power level of 15000). That's fine so far, but consider the wear on the bow as well