Good Day psukbat,
Thanks for reaching out, and Happy 2019 to you too.
The reason why we do not cut out door frames is because you or the builder will actually need to buy this timber to be able to construct the project. However, if you wish to remove this bottom plate, you will need to click into the wall framing until you can edit it, then manually remove the timber in the opening. Could you please try this and let me know how it goes?