I don't subscribe to traditional fishkeeping rationale.
amen to that!
there are to many people that are being told that you cant have more than 1" per gallon when infact this is a guide, they just go OTT
There are MANY different schools of thought in every aspect of fiahkeeping and NOBODY has it right
While internal filters and box filters are common in the UK, they are not used in the US. Then in asia, they use mainly OHF, which are amazing and underrated filtration systems, but not really used anywhere else. Also "overstocking" tanks is a common and highly successful practice in asian countries, but shunned in most other parts of the world.
No single school of thought has it right, so its really up to the individual fish keeper to either follow the reasoning they're given in their area, or research for themselves and come up with a system that works for them and their wet pets.
The 1"/gallon "rule" is set up as a basic guideline for new fish keepers with no knowledge about water parameters, nitrogen cycle, advanced filtration function in regards to beneficial bacteria, etc.
Its a basic guideline someone decided was a good idea a long time ago, and while it still serves its function for beginner fish keepers, it is not gospel etched in stone, simply a guideline.