MacBook blank screen when lid is open to 90 degrees

i mailed my 2016 MacBook Pro to the repair center to replace the screen for free because there is a display backlight service program. And then the technician came back to me and said they found another issue: liquid damage into the battery and I have to spend more than $600 to repair it before replacing the screen. Either decline it or accept the new quote ($618 + tax). It does not make sense because my MacBook is working fine and I don’t see any issue with the battery or charging. Why does Apple force me to spend $600+ to repair something that doesn’t exist or stop me from using my MacBook before fixing the real issue? I am so disappointed!!!