The only legitimate reason why the traces would be joined if they are both" netted" the same e.g. named "Gnd" or "0V". Sorry, can't comment on the "patch" but V15.0.4 seems to be OK with the tracking issue you describe.
Best to avoid using Powerplanes as some areas can become "fragmented" due to a high density of vias and this is not picked up by the DRC. Use area flood pours instead. (with thanks to Iain on this issue).
Sounds a bit like the copper pour on internal layers shorting problem, but that was fixed in the last rev I think .... the "copper pour verification" check in the Design rule dialogue.