How does the location of the undercarriage affect 'Nosing Over'?

"The location of the undercarriage and the height from the ground of the aircraft’s centre of gravity have a very important
role in the design of aircraft. In the case of a “tricycle undercarriage” the main wheels are situated at such a distance
behind the centre of gravity that its projection at take-off and landing angles of attack (plus a safety margin of 2-3 degrees
do not fall outside the line joining the right and left supports. This prevents the aircraft from nosing over and provides
stability during the landing run." __Page 13,Theory of Flight

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It can be easily understood that in a Tricycle configuration, if CG(or its projection) is aft of supporting main wheels, Tail Strike can happen. And in Tailwheel configuration, if CG(or its projection) is forward of supporting main wheels, then ‘Nosing Over’ can happen. But the line "In the case of a “tricycle undercarriage” the main wheels are situated at such a distance behind the centre of gravity" and line "This prevents the aircraft from nosing over " is contradicting.