Yes - but TV screen sizes are advertised in diagonal length because it is assumed an aspect ratio of 16/9. For a given aspect ratio, larger diagonals imply larger area.
There is a host of aspect ratios for pc displays, 16:10 and 16:9 are both quite popular. Guess what? Nobody runs around looking up screen area.
I have a 16:10 display, which is 'bigger' (visually) than a 16:9 of the same diagonal length when working/playing and bloody 'tiny' when watching videos.