New capability almost never replaces what an organisation runs today. It has to reach into systems that predate it, some of which nobody fully understands any more, and it has to keep working while those systems change underneath it.
Design the seam deliberately
A normalisation layer above the systems you integrate with is worth its cost the second time a supplier changes. Coupling directly to one vendor's payload shape is faster to build and turns every later change into a rewrite.
Own the record
History that only one supplier can read is a commercial position dressed as an architecture. If the operator cannot take their own data with them, the integration was designed against their interest.