krias shema

Question

I assume the reason you say that myzmanims zman krias shema is wrong is because their netz is off by 2 min. If I remember your fathers teshuva correctly, your father says that it's a safek which zman is correct, and since the inyan of vasikin is zrizin makdimin limitzvos, so pushing it off 2 minutes for a halchchic concern that you might daven shemoneh esreh before the zman, would not be violating that. However when it comes to zman krias shema this whole cheshbon shouldn't apply bec. saying krias shema 2 min before the zman ends would not be a problem? Thanks.