I think del backed a yew bow with another staves yew sapwood.
And then boo backed the other naked stave.
If you want to sacrifice a perfectly good yew stave for bamboo backed that's fine.
But to answer the original question. Under usual circumstances bamboo backed yew bows are yew heartwood backed with, of course bamboo. The only thing to worry about really is the supplier of bamboo selling you the proper material. I get my moso bamboo from echo.
Let us know how it turns out