I am currently three months into writing a Master's thesis for a Master's degree in Mathematics, and the school I am currently attending is a California state university. I was asking my thesis advisor if I can expand the scope of the topic of my thesis, which means I would have to anticipate 2 years of working on the thesis (instead of 1 year).
However, as I am also applying to various math Ph.D programs after completing my Master's thesis and degree, my thesis advisor is not keen to the idea of working on a larger scope of my thesis for 2 years. My advisor says that this would be "inappropriate", that he thinks the faculty on admissions committees would be confused and that my advisor would "not be doing his job" (in having me finish in 1 year, or "soon enough").
I for one disagree with my advisor personally, because I thought that expanding the scope of my thesis, even if it would take longer for me to complete and defend, would look even better on my Ph.D applications. I thought this would actually impress the committee rather than confusing them. I wanted to demonstrate that my finished thesis would reflect my having looked into more mathematical papers in research literature, as opposed to only two papers, which were chosen by my advisor, that I'm reading currently for my thesis topic.
So I'm asking here simply for more thoughts on this matter. I do hope my point is valid, but if it seems most of the people here are agreeing with my thesis advisor, then I'll understand either way.
tl;dr: I want to write more to my Master's thesis and plan to take 2 years instead of 1 year. My advisor disagrees and thinks the Ph.D admissions committees won't like this. Is this true?