Giving tied places feels like a cop out for me. Otherwise we should do it for many other years IMO.
As for who was #1 in 1970. I suppose it would make sense to defer to the experts. Not reaching a QF is a blemish but Laver has a lot of plus's in his corner as well. Were these rankings from the 1970 itself or done after the fact?
NatF, You may feel it's a cop out. I feel it's unfair and illogical to decide in every year and at every place who was the better of two players (or even of three players). Life and mathematics tell us that sometimes two or three players have records where it's not possible to exactly distinguish which player had the better one. Look at 1959: Gonzalez or Hoad? 1977: Borg or Vilas or Connors? As you know there are experts who decided it was Pancho. Others who decided for Hoad. The same regarding 1977. All of them have good arguments for their favourite.
Even Lance Tingay who never split regarding first place, sometimes put three players equally on tenth place. I never understood his logic by the way.
Yes, we should do the splitting for several or many years. I give tied top places for 1930, maybe 1931, maybe 1936, maybe 1937,(the last three after reading some arguments from krosero), 1938, 1947, 1952, 1959, maybe 1960, 1961, 1964, maybe 1965, 1970, 1971, 1972, 1973, 1977, 1982. I have not studied later years. My list sounds very long and strange but, for instance, are you able to decide if Smith or Nastase (won US Open and lost to Smith at Wimbledon in a five sets final) deserves the No.1 place? Can you differ between Connors or Lendl in 1982? I can't do.
Regarding 1970 it might be a blemish for Rosewall and Newcombe winning much less tournaments than Laver but they can argue that they succeeded at the two events that (by far) mattered most. Thus Tingay and Collins, the men with the greatest reputation among the tennis experts of that time, ranked Laver No.3 and 4. I'm between them and the majority of the TT posters. Maybe not too unfair...
Tingay's and Collins' rankings were compiled in 1970.