Although ... if I am shown just the base view of a range of Paul Ysart weights, I could probably say for most, with a fair degree of accuracy, whether they were 1930s, 1930s/40s, 1950s, 1960s or 1970s!!
But that sort of age-related identification is a specialist field (which anyone can learn in time), so it's not really pertinent to the general question of whether a pontil mark, or lack of, can determine age.
It would be good to one day show a few web pages of "typical" base finishing for all sorts of weights, antique to modern. This is something that is so often neglected in the literature yet, as rightly sated by others, the base finish of a weight can be a major clue towards an attribution.