I suppose it's how deep the stumps are ground. Two feet is possible. Clean out the hole and add nearby soil and plant away. Use the stump grindings as mulch. I've done it.
As an aside without a stumpgrinder, I have cut trees down as low to the ground as possible and then covered with a few wheelbarrows of soil and then planted groundcovers. Also, a very low stump makes a good place for a compost pile if it's in an out of the way place. Add a little fertilizer occasionally and the stump decays faster.
Another treatment for a stump is to add a little topsoil and then some Sedums.
Mike
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The tall stump was used for a block and tackle to yard my kid's old truck out of the woods so he could haul it away.

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This stump was just planted this winter so it hasn't had time to fill in yet.

The only problem with leaving stumps intact is if you have honey fungus on the site. In which case, there can be quite a problem if stumps are left whole near other plants, especially woody ones.