Rows aren't faster. Squares are slower. In Minecraft, Java Edition, a crop doesn't grow on a timer: about every 68 seconds, night or day, the game picks it at random and it rolls to grow one of its seven stages. Wet farmland under it and around it gives the best odds, one in three.

Then it checks its neighbors. The same crop beside it in one row is fine. The same crop beside it both ways (east or west, and north or south), or on any diagonal, cuts its odds in half, to one in six. In a square of one crop, every plant is halved. In stripes of wheat and carrots, not one is. Different crops don't count against each other, and empty farmland between the rows works too.

The same halving is in Mojang's code from the June 2010 Infdev build to today's Java Edition 26.3. The numbers here (one in three, one in six, 68 seconds with the default random tick speed of 3) are 26.3's.

The farm, the timing and the time-lapses are our own simplified version, drawn in code: each plant's stages follow our own run of the game's rule on these two fields, shown sped up.

So a checkerboard of wheat and carrots: fast or slow?

Sources: Minecraft Java Edition, the game's code in Mojang's releases Infdev 2010-06-18, Beta 1.7.3, 1.8.9 and 26.3: CropBlock, FarmlandBlock, GameRules, ServerLevel.
Not an official Minecraft video. Not approved by or associated with Mojang or Microsoft.
Sounds and music: our own, made in code.