Is a brick with a smaller Lego logo real?
Many sets have had mold changes over the years, as they get slightly redesigned, or even just wear out. I would rest at ease.
It's the old pieces that don't have ANY markings that say Lego that always worry me.
Edited: I took photos of two Duplo train track pieces I noticed today. I merged them together to show the scales are (very close to) the same, yet the logo sizes are quite different. I also included the untouched photos for completeness, and because they're easier to read.
In summary: Lego changes their logo size on the same part.