A family of Microsoft word processing software products for creating web, email, and print documents.
With respect, that procedure adds a plain text legacy forms control, which is not a content control. If the OP actually wants a content control
a. they should be aware that in version 15.40 there are no facilities in the user interface or VBA to add them. modify properties such as title, tag etc., or connect them to the XML datastore.
b. it is easier to do it in Windows Word as Charles said. However, if that is not possible, John Korchok posted a document containing sample content controls of every type except the repeating group controls at https://1drv.ms/w/s!AuMdOB79OSNjhW65F4-K-7f6tuGY - the controls can be copied and pasted from there. (see https://answers.microsoft.com/en-us/msoffice/forum/msoffice_word-mso_mac-mso_mac2016/why-cant-content-controls-be-created-on-a-mac/758cde5a-42e3-45f6-b367-fd4c9e7d5cd2 for John's original message).