Risk control of bottom up approach

CFA Level III Derivatives
#1

In Schweser vol2 practise exam, exam 1, afternoon session, it asked:

Which of the following strategies least likely to enhance Risk control of bottom up investing approach.

Contrarian is the advert. The other two are overlay approach and blend of bottom-up and top down approach.

My question is that why a top down strategy would enhance Risk control of a bottom up strategy?

#2

By using top down with bottom up, you can have a different view point which can help confirm or reject your current viewpoint. If topdown gives you the same suggested strategy, it is good affirmation. If top-down suggests doing something otherwise, then you have added some risk control.