Correct geometry is the line in the sand between going out there and riding a pattern, and actually understanding the correlation between correct work and how it affects how the horse can move up the levels.
Now, for us mere mortals, especially at the lower levels and with young green horses, early days in the show ring are as much about survival as they are about the training scale, and sometimes the perfect circle gives way to staying in the ring:)
Bit you won’t see incorrect geometry if you watch well scoring tests at higher levels. You can’t get there without it being right.