Page 66 of the SEC Men's Basketball Media Guide lists the SEC Champions for each year. Yes, all four of those schools were listed as champions for 2000. There are no tie-breakers for regular season champions in any SEC sport. (Except for football, sort of. If you tie for the division title, you have to win the tie-breaker to have a shot at the conference title.)
Copy/paste from the media guide: "From 1933‐50 the SEC Champion was determined by a tournament, except for 1935. Since 1951, when the round‐robin schedule was introduced, the title has been decided by a winning percentage on the conference schedule. From 1951‐64 the round‐robin consisted of 14 games. In 1965 and 1966 it was expanded to 16 games. From 1967‐91 the round‐robin schedule was 18 games. In 1992 the SEC split into an Eastern and Western Division, but continued to recognize an SEC Champion based on a winning percentage over the 16‐game conference schedule. The league also began awarding division championships. In 1979 the tournament was renewed with the winner receiving the SEC’s automatic bid to the NCAA Tournament."
Side note: It took me three attempts over several hours to download this stupid thing. The SEC website sucks.