In Inventor 2019, a new “Lock Hose Length” feature has been added to the “Edit Hose Length” option. In the previous versions of Inventor, the length of the flexible hose provided in the Actual Length field of the Edit Hose Length dialog box was not a reliable indicator of length. Whereas, the new Lock Hose Length allows you to calculate an exact sum of hose length.
When selected, if components move or shift, this option prevents the length of the hose from changing due to adaptivity. Lock Hose Length allows you to calculate an exact sum of hose length.
Once you do that if you check the Edit Hose Length window, you will see that Lock hose length option is turned on automatically, explaining, that added dimension has locked the hose length.
If you clear the option, placed dimension to a flexible hose will convert to a driven dimension.