I am going to agree with you, with reservations.Inspiration yes, but mode of inspiration is not an essential doctrine.
I believe there are at least 5 theories extant in Christendom today regarding the mode or method of inspiration.
1. The Intuition or Natural Theory is held by the typical Modernist. This person believes that inspiration is merely a higher development of that natural insight into truth which all men posses to some degree. In other words, the Bible is merely a book by men with highly religious motivation, and is similar to a book about science written by men with highly scientific motivation.
2. The Illumination or Mystical Theory regards inspiration as merely an intensifying and elevating of the religious perceptions of the believer, the same in kind, though greater in degree, as the illumination of every believer by the Holy Spirit. This position holds that the Bible is not the Word of God, but only contains the Word of God, and that not the writings, but only the writers were inspired.
3. The Dictation or Mechanical Theory holds that inspiration consisted in such a possession of the minds and bodies of the Scripture writers by the Holy Spirit, that they became passive instruments, not participating in any way in the process of inspiration.
4. The Dynamic or Conceptual Theory states that inspiration is not simply a natural, but also a supernatural fact, and that it is the immediate work of a personal God in the soul of man. This theory holds that the Scriptures contain a human as well as a divine element, so that while they present a body of divinely revealed truth, this truth is shaped in human molds and adapted to ordinary human intelligence, and is thus conceptual (the idea, or thought, or concept is inspired) rather than verbal (the very words are inspired) in its view of inspiration.
5. The Verbal and Formal Inspiration position believes that first of all the Holy Spirit worked in the Prophets of the Old Testament and the Apostles of the New Testament in such a way that the very words of God were selected from the vocabulary of the man, taking into account his culture, education, and experience, and that not only the very words, but also the forms of the words, such as noun, pronoun, verb, adverb, singular, plural, etc., were written at the prompting of the Holy Spirit.
Proponents of numbers 3, 4, and 5 could probably be found within the parameters of conservative Evangelicalism. So in that respect I agree. The adherence to a single "mode" or methodology is not an essential doctrine to be included in the ranks of conservative Evangelicalism, but numbers 1 and 2 would, in my opinion, exclude the person from those ranks.
That can be seen on this very forum. Many of us are staunch defenders of position #5 while others defend #4. (I am not aware of any who accept #3 on the forum.) Yet both consider the other to be within the ranks of conservative Evangelicalism. I am a Theologically conservative fundamentalist (not the new, revisionist use of the term, but the original meaning, one who believes the 5 fundamentals of the faith, one of which is the inerrancy of the scriptures) and consider both #3 and #4 to be in error, but still consider those believing such to be my brother/sisters in Christ, fellow laborers in the Gospel, and fellow travelers on our Royal Path of Life.