Long ago they loosened the entry requirement for betting. Previously, horses trained by the same trainer had to be entered as an entry for betting purposes. Horses from the same barn continued to be entered as entries. It is also not unusual to have an entry from the same owner composed of a front runner or pace setter to set a face early pace for a more seasoned entry mate.
The issue in this race is that one of the entries “blocked” a lane. In a small field that this was, it is a ludicrous argument especially given a mile and half race. Yes it did look like the Indy horse forced a horse wider than they wished for it to run. A jockey is paid to be careful not to have it happen. Justify was the better horse on Saturday. If someone lost it was poor racing luck, nothing more.
What “they”?
There are numerous jockey clubs all over the country with different rules. Think of states’ rules vs. universal federal rules. Racing has no one rule.
We still have many couples requirements. Sometimes I think it even varies from race type to type. It may be these TC and BC races withdrew that rule but you cannot say this universally either way.