This is a regular sound change
In Coastal Yue, MC’s TSY- and TSR- series all become *Tɕ **except** in the specific condition of *TSRI-type syllables where instead they become *Tsɿ
there are only two exceptions i've found so far, both where LMC ʂ(ɦ) > TS ɬ where we would expect s.
the exceptions are:
師 (srij /ʂij/ > lhu1) 'teacher, master'
事 (dzriH /ʂɦî/ > lhu5) 'thing, task'
not sure what's up with those but otherwise the correspondence holds!
This distinction is lost in Cantonese but if we compare for example Nanning Baihua, a variety closely related to Cantonese:
思 sɿ55 < si
市 ʃi24 < dzyiX
師 sɿ55 < srij
Noting that MC ie, ij, i all merge into /*i/ in “Common Dialectal Chinese”
This isn't bad because it's worse than things various Western states have done, it's bad because it is remarkably similar to policies like Canada's residential schools that most decent people now recognize as moral abominations.
“People all raise their children expecting (them) to be smart;
I was hindered my life by smarts;
(I) only hope that (my) child is stupid and rough;
(so that he can) become an official without trial or tribulation”