While as discussed in Gordon's and my exchange, above the degree of accuracy in surveys such as the one which is the subject of this thread, is likely not wonderfully high; I can accept their giving a meaningful indication of tendencies.
An interesting feature to me of this survey, is the Czech Republics coming in second place for number of kilometres of line per 1,000 square kilometres. One trait of Cold War-divided Europe was the tendency of Communist-bloc countries (both from policy, and from economic necessity) to use rail transport more, and road less, than their Western counterparts. Though this has varied somewhat between different Eastern European countries; some of same kept in use to a late date, far more of their rail systems as at peak, than did the more rail-forsaking of their West European contemporaries.
The East European country which I know best, is Poland. When I first went there in 1980 it occasioned delight on my part, that the Polish State Railways then active passenger network was, at a guess, on approximately the same level re lines still in passenger use, as British Railways had been around 1955 innumerable rural local lines still with passenger services, and a good number of lines above and beyond this, which had lost their passenger services but still carried freight. The same seemed from the published timetable, and from a couple of first-hand visits which I made to go for Polands neighbour Czechoslovakia. This situation continued pretty much to obtain in Poland, until the end around 1990, of the overall Communist-bloc situation. A couple of years later, massive bouts of passenger-service withdrawals on lesser rural lines in Poland began, and carried on year after year the picture is also got, that freight use of such lines has very sharply declined. In the surveys km. per 1,000 sq. km. league table, Polands figure is 62: three points lower than the UK.
The Czech Republic, on the other hand, scores 121 which would seem to indicate that the Czech railways have kept in service, a large proportion of the lines which they had thirty years ago. Its nearest competitor in Eastern Europe Hungary rates a very significantly-less 77. The figure for the Czech Rep.s now-separate sister nation Slovakia is slightly less still, at 74. While my impression is that Slovakia is a bit wilder and hillier than the Czech Republic hence figurably a bit less, ever, in the way of railways it always struck me that in Communist times, the area was amply-railwayed in its own right. Suggesting a scenario of a lot of rail closures in Slovakia in recent decades.
All this promotes thoughts of potential pleasant visiting of the Czech Republic for a time-warp feast of country-branch-line travel, albeit with modern traction...