Hmm. Perhaps I'm missing something.

Even if we are talking about the Log File... not the log backup... unless there was a subsequent Shrink Operation, it certainly will NOT be smaller. There is a fair chance it'll be the same size... and the question asks COULD it be bigger?

It could be the same size, or bigger... but nothing says it HAS to be the same size (unless someone turned off autogrowth.)

For me, I interpreted the question to be able to backup files of the transaction log... so I didn't even start thinking in these terms until I'd seen what you folks had written. 😉