The Supported Upgrade Paths to Microsoft Dynamics 365 Business Central Releases document from Microsoft was updated with a note in late October to reflect a change to the upgrade path for Business Central 2019 (v14), starting from 2025 release Wave 1 (v26).
This change will affect the upgrade to Business Central 2025 Release Wave 1 (v26) which will now require you to upgrade from Business Central 2019 (v14) to Business Central 2024 Release Wave 2 (v25), before doing a second upgrade to 2025 Release Wave 1 (v26).
There is also a note that upgrading from minor updates between the release updates might not always be supported; you need to check the Dynamics 365 Business Central Upgrade Compatibility Matrix to check if the version you’re on is compatible and upgrade first to a supported release before continuing the upgrade to a later release.
As time goes by, I expect that the upgrade path for older versions continues to become longer with more versions needing to upgrade to an intermediate version before upgrading to the most recent release.
This is probably more the case with versions of Microsoft Dynamics NAV, of which all are no longer supported, but will impact earlier versions of Business Central.