it is not possible to say what everyone means when they say a number. some are just spamming, some are repeating like a parrot, some have their own analysis.
for example the $20k is more of a mental barrier that people set for themselves and it is more virtual than be real. it has always been the same with all previous ATH prices.
some other numbers such as $100k and $1 mil are mostly round numbers and with some extrapolation of data from the past 10 years accompanied by some technical analysis we can get there while rounding the price to the nearest round number such as $100k.
$70k i'd assume is the same with a little bit of pessimism included.