Honestly, Jesus having a sinless mother would detract from Jesus, not add to him.
“For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin.”
And that includes the temptations that rise from having a sinful mother.
“ Honestly, Jesus having a sinless mother would detract from Jesus, not add to him.”
It’s about exalting Mary into a demigoddess
Being sinless gives her top rank in the Roman Pantheon of Demigods and Demigodesses.
And a whole passel of brothers and sisters.