I understand why you want to just follow what others did before you. It is extremely hard to say to your colleges that what they did might not be the best option.
For small connectors (<20 or so pins) i could even see a benefit to doing it this way. (If i squint very hard.)
It might even make sense to do it for larger connectors in pure flat designs. But even here i would say that there is a limit how large a connector can be for this making any sense. A much better solution would be a project specific symbol that groups pins into logical units as needed.
In hierarchical design (which is what kicad excels at) i would say that it is a bad idea in general to have the connectors pins split over many subsheets. (Which is the only usecase i see for even wanting it as separate units in the first place.) My reasoning is that such a connector would create knowledge dependencies between otherwise independent systems (it is comparable to a global label in this regard.)
I also guess that very high pin count connectors can be abstracted as a much smaller number of buses. So i would probably make a subsheet directly under the system level abstraction and have a number of bus entry pins for this sheet connected to the connector pins as needed.
The buses are then connected to the other systems at this system level as needed. (Yes i am aware that buses are kind of restricted in kicad version 5. This will become much more powerful in version 6.)
For more details see: Hierarchical or flat schematic design, what is best for me? (How to deal with multi page schematics?)