Maha has actually raised that value to 0.5C instead of 0.33C to ensure a good delta-v detection in later documents.
Super slow charging, such as done in break-in mode, is so low current that no delta-v can be detected, so it relies upon a typical timed slow charge cycle in break-in mode to quickly bring new or neglected batteries up to full capacity. You can do the same by merely using them for a few cycles. Break-in just readies them faster.
Super slow charging is usually recommended by battery manufacturers since they can not individually vouch for the accuracy of each and every fast charger out there. Fortunately Maha is very accurate with the C9000 as long as you supply 0.5C to 1C or thereabouts to get that delta-v. Super slow charging is also the easiest and cheapest way for consumer products to get batteries charged by just using simple timing.
This does not actually mean that super slow charging is beneficial with modern batteries. Batteries from this century have much less internal resistance, and can handle faster (not super fast) charging, however the urban legend about slow charging is just too established from users who used batteries in the 80's.
If you look at Sanyo Eneloop documentation intended for commercial users / oem's, you'll see that 1C actually nets you the best cycle life, provided you use a quality charger that detects delta-v accurately.
Since 0.5C is the real minimum, the "no man's land" between a break-in current of typically 0.1C to a minimum of 0.5C for normal charging will actually present the most risk.
Don't forget that Maha C9000 will give you a value for internal resistance upon the first insertion of the cell, and this value is shown only once - thereafter the cell voltage, and not the internal resistance value will be displayed. You can determine if you are using some cheap, damaged, or otherwise neglected cells:
1.6 - fresh new battery
1.8 - middle aged yet still usable
2.0 - old aged, high in internal resistance, lowered capacity. Time to recycle.
2.2 - Maha will refuse to charge.
Some may be tempted to get around the refusal to charge cells with high internal resistance by putting them into a dumb slow-charger. Not smart - the battery is more resistor than battery, and now you are headed for a problem. Heed the warning by Maha - it is there for a reason.