I have came across this reference: https://www.e-education.psu.edu/styleforstudents/c3_p35.html
This phrase is virtually meaningless, but we often hear it on the news and in bloated speeches. “In terms of” is really just a wordy and sloppy transition—usually an unoriginal disguise for a simple preposition, such as “in,” or a more elegant phrasing, such as “in relation to.” “In terms of the cost, it is high,” is easily revised to “Its cost is high.” Do not use “in terms of,” or do so trembling.
Is the reference really right?
Can I use the following sentence?
The figures are expressed in terms of a percentage/in percentage terms.
If so, the phrase "in terms of" seems not to be referred to relation.