This feels like a motte/bailey tactic. I remember clearly being taught the equal-transit-time theory as a kid, and it was taught as actual fact, not a simplification. I was uneasy with it but couldn't vocalize why (it didn't occur to me to ask why planes can fly upside down).
If it is meant as a simplification, many HS teachers have not gotten the memo.
If it is meant as a simplification, many HS teachers have not gotten the memo.