Most of those calculators are based on commercial systems, and are designed to result in a flow rate around 128oz/min. This works ok for most commercial systems because they're all kept under 36° and the carb level is always at or under 2.7 vol. If you're going to serve your beer warmer, or have a highly carbed beer, or don't have a perfect tower cooling system, using those calculators and equations will usually result in a foamy pour. Temperature is the big one, as just a few degrees will cause the CO2 to come out of solution if the pour is that fast. The only side effect to longer lines is a very slightly slower pour.
Many of those caclulators and articles about line balancing reference the "ideal" line length. IMO a longer line that takes an extra second to pour a pint but can serve beer at a wide variety of temps and carb levels is a whole lot more ideal than a line that pours just as fast as possible without foaming when everything is perfect, but results in a foamy mess the rest of the time.
FWIW the only line length calculator out there that doesn't ignore the basic laws of fluid dynamics is this one. For cold temps I'd use at least an 8 sec pint fill, anything up to 42° I'd use a 10 sec pint fill speed, and even slower for warmer temps-