If this is expressed through equations, then the current initial wave has slightly different initial values of the variables.
Namely. Until spring 2017, Bitcoin held about 80% of the market. Now it is 50-60%. In addition, many new altcoins have now appeared, some of which are dying and some occupy a market share. Now the behavior of altcoins may be different.
"The equation changes completely" was only an expression...
However, although I don't know the number well, you're right: most of the information on how the altcoins behave is based on what happened in the past, when the market looked different: the altcoins were more alive.
Now the overall situation may differ (although some altcoins are still very strong).