⚡ represents the LN network. Sats are a the smallest unit of account for Bitcoin. The two are closely tied but not the same. It'd be like using the $ symbol for VISA. When pricing items in Bitcoin becomes commonplace, if ⚡ is what people use on pricetags etc., I'll of course gladly adopt that standard.
Discussion
Whilst you're technically right, realistically speaking most people likely see Sats and LN go hand in hand the same way they see BTC and the Bitcoin Network. Thus, ⚡ is a more appropriate symbol for Sats.