Well... No. You're reading the title. Read the document.

"We all know" is the gateway to ignorance. You need to test common knowledge to see if it's really true. Just assuming it is isn't knowledge, it's guessing.

Second - it's not always true:

for the fasta benchmark, Fortran is the second most energy efficient language, but falls off 6 positions down if ordered by execution time.

Thirdly - they also did testing of memory usage to see if it was involved in energy usage.