market-oriented style

Hi , all simple question; Why “market-oriented style” resembles broad market index?? thanks in advance…

It could use a combination of growth and/or value style and tries to build a portfolio. In the market portfolio the stocks included generally follow the overall market and are neither value nor growth.

some problems in CFAI text point to a gradual dilution of the portfolio from strongly tracking value ( or growth ) style to less and less of the tracking , signifying a leaning towards a market-oriented style