Ok, but the president's executive order does not officially change the name of a place or feature. In the US, that function is overseen by the Board on Geographic Names. While they did enact a change for the Gulf of Mexico (now the Gulf of America in US documentation), it doesn't happen immediately. While I imagine the BGN will update Lake Ontario eventually as well, Google tips their hand as being eager to please the admin by updating their maps before there is a corresponding change from the appropriate governing authority.

We can't even accuse Google of consistency, because they show Türkiye as Türkiye, for example, even though (as far as I can tell) the US Gov still uses Turkey.