Not sure how that person you talked to calculated his safety pilot time, but to clarify a little;
The average flight during your cross country phase is 2.5 hours, or thereabouts. (The total cross country time working out to about 75 hours.)
Now, the pilot flying (PF) will log the full 2.5 hours. The pilot not flying (PNF), or safety pilot, would log about 2.0 of those hours, as the PF obviously do not stay under the hood while starting, taxiing and doing run-up and so on.
This works out to be about 33 trips. (Again, working averages.) 16.5 of those would be as PNF, working out to 33 hours or so. 16.5 would be as PF, working out to 42 hours.
To a total of 75 hours.
Not that it makes a big difference between 30 and 50 hours of safety pilot time, but.. I'm a stickler for detail.
Cheers,
Helge