We are dealing with the same problem. We added all of the product fields to the Product Main form and published it. Even after this, we are still seeing the same warning message.
In this case, we also tried the Microsoft support solution. I'm not sure if we did everything correctly. The steps are outlined below.
1. Created a new solution and only included the Product Main form.
2. Exported this solution as Unmanaged solution.
3. Under customizations.xml page added the mentioned code under existing parentproductid row.
4. This is the existing XML node.
<row>
<cell id="{75ac24ed-a31e-a1e4-dbd5-3c38e6b42ab4}" showlabel="true" locklevel="0" colspan="2" ordinalvalue="10003" solutionaction="Added">
<labels>
<label description="Parent" languagecode="1033" />
</labels>
<control id="parentproductid" classid="{270BD3DB-D9AF-4782-9025-509E298DEC0A}" datafieldname="parentproductid" disabled="false" uniqueid="{9c61b774-c7a1-cb9e-210b-a926b543b4cc}">
<parameters>
<AutoResolve>true</AutoResolve>
<DisableMru>false</DisableMru>
<DisableQuickFind>false</DisableQuickFind>
<DisableViewPicker>false</DisableViewPicker>
<DefaultViewId>{8BA625B2-6A2A-4735-BAB2-0C74AE8442A4}</DefaultViewId>
<AllowFilterOff>false</AllowFilterOff>
</parameters>
</control>
</cell>
</row>
5. Added the additional node in customizations.xml below the above existing node.
<row>
<cell id="{faaa2942-4737-4721-9a19-7dcbf4eb2911}" showlabel="true" locklevel="0" colspan="2">
<control id="editableParentControl" classid="{270BD3DB-D9AF-4782-9025-509E298DEC0A}" datafieldname="parentproductid" disabled="false">
<parameters>
<DefaultViewId>{19d7f2e0-e427-40fb-85e8-53e7cef2b166}</DefaultViewId>
<IsInlineNewEnabled>false</IsInlineNewEnabled>
<DisableMru>true</DisableMru>
</parameters>
</control>
</cell>
</row>
6. Save the changes, zip the solution files, and import the new solution in the organization.
7. Publish all changes and navigate to the Product form; the message remains on the screen.
I'm not sure if this is what was required or if we did it incorrectly. We'd appreciate it if you could correct us or point us in the right direction.
Regards,
Mahesh