My Rabbi told me simply that if one does pronounce the shma properly like it’s written, one is not yotzei his obligation of kriat shma. For example the first word in the first paragraph of shma is ואהבת, one can pronounce is it vey-a-ha-vta or vey-oh-ha-ta, difference is “and you LOVED you G-d” versus “and you should LOVE your G-d”. Big difference? So my question to you is does it make a difference to pronunce the kometz like it’s written or not?
The general rule with saying shema is that if he didn’t say all of the words and letters, but he skipped some, then he didn’t fulfill the mitzvah, however if he said them all, but he didn’t say them correctly and properly then although it isn’t the correct thing to do, he fulfilled the mitzvah. Therefore in this case he was yotze.