No, as stated in the PHP documentation I linked to, it means
session.gc_divisor coupled with session.gc_probability defines the probability that the gc (garbage collection) process is started on every session initialization. The probability is calculated by using gc_probability/gc_divisor, e.g. 1/100 means there is a 1% chance that the GC process starts on each request. session.gc_divisor defaults to 100.
My take is that 1% is low, but depending on how often a SESSION is started the odds are higher. that a SESSION will be GC’d
Not as clear cut as Java GC but maybe a bit more than JavaScript GC