On the occasion when I've been in a position to offer investing advice to beginner investors, I've recommended a portfolio closest to a Bogleheads
three-fund portfolio given the choices available to the investor. This is the case even though I myself like to tilt to small-cap value, and even though I prefer intermediate treasuries to Total Bond Market. I do this to keep my recommendation as simple and conventional as possible.
Recently I've been helping my girlfriend of a few months with her 401(k). She has been very receptive to my advice -- one of the many reasons she is awesome.

She has an outstanding 401(k) with many exceptionally low cost passively managed funds from Fidelity, Vanguard, DFA, and others. There are excellent options to tilt to small-cap value and intermediate treasuries. Even so, I recommended she go with a three-fund portfolio for the reasons above. She took my advice.
I'm wondering if this recommendation was a mistake. If I truly believe that a tilt to small-cap value and intermediate treasuries has a slightly higher
expected risk-adjusted return than a three-fund portfolio, should I recommend it to beginners as well? I'm curious to hear from others who have been in this position.
Avi