SC: Comparison. Do we need 'that of'?

[ZuyueZ224]

In OG2018-SC-758, there is a question:

[Problem text deleted because it's from a banned source. Please make sure to read and follow the forum guidelines before posting.]

The answer is: Prices at the producer level are only 1.3 percent higher now than those of a year ago. So we have a "those" in this sentence.
But I remember Ron once said in a video that
right: Gas prices in 2007 were higher than those in 1997
right: Gas prices were higher in 2007 than in 1997.
wrong: Gas prices were higher in 2007 than those in 1997.

So in the sentence "Prices at the producer level are only 1.3 percent higher now than those of a year ago" shouldn't we just remove "those of "?

[ZuyueZ224]

I guessed RON have answered questions like this. There is his answer:
https://www.manhattanprep.com/gmat/foru ... ml#p117480
https://www.manhattanprep.com/gmat/foru ... 31036.html