Frogs prefer to pathfind through water than over land, as they swim faster than they walk. However, this is not true if the land contains open doors.

In the setup shown below, I spawned a frog on the quartz platform and moved backwards while holding a slimeball. I used a /tp command to ensure I was lined up horizontally in the exact same position each time. The frog consistently chose to go through the water if the grass had no doors on it, but over land when the open doors were present.