...Those staves are pretty straight!
Following the grain is important with some woods, no so much with others.
Look at it this way, a bow is tapered (generally) so you are going to go across the grain to some extent.
With Yew and I'd suggest Hickory, Elm and some others, the amount of run out on those staves is minimal.
It's a matter of degree.
But on the other hand, they are so straight you may as wall follow the grain and have a little waggle here and there.
As long as the ends and the middle line up, a few waggles don't matter. Leave the tips wide until the bow is back to about 3/4 draw and braced, then you can adjust the tips to correct the string line if needed ( or make a slight heat correction)
Ram rod straight bows are a bit boring.
Here's a couple of staves that really need steam bending to get 'em straight.
Del