I suppose in layman's terms you're correct but at the same time... not. Simply, the /ts/ in Japanese is something called an affricate, which is a stop (k, g, t, d, p, b) combined with a fricitive (f, v, s, z, sh). There are two affricates that I know of in English; /ch/ and /j/; yeah, j. The /j/ in English is actually the combination of /d/ and /j/, the /j/ being the one in Japanese (a "soft" J). Meanwhile Japanese has the two classic /ts/ and /ch/. The reason it's explained as a "soft" j or s in English is because a sound that isn't in one's native language in always harder to tell apart without getting used to it. Japanese has double consonants (fricatives and stops) and double vowels; both of which are more difficult to tell apart from normal consonants and vowels. This is the same with diphthongs (two vowels flowing into eachother) in Korean, this is another example. Though probably the weirdest one IMO is that any time a vowel is the start of a sentence (or a word) it will have a glottal stop before it. English speakers have no clue they're doing it nor how to not do it without practice.
I suppose that wasn't simple, nor short but maybe it illustrates what I mean or taught someone.
TLDR: /ts/ is a bit difficult to say or tell apart from /s/ as an English speaker so it's described as a hard /s/ as to make it easier.
Sorry for babbling, I'm not trying to be offensive if that's what it seems like; I just like language (;;-;;' )y
Have a nice day/night/evening/whatever.