I has very curious about this Feature and put in a support ticket to get it enabled on one of my own apps.
The product manager did enable it for me and I had some dialogue with him where he gave some explanation as there is not currently a Knowledgebase article anywhere.
Here was the email I sent to the PM.
I just tried it and it�s very intuitive. I have a form with tabs and they do not load until I select the tab. But once I do select the tab, then the data �stays loaded�.
I think that this would be a great feature to roll out in a self serve basis where the Admin could set the app properties on how to behave. It could be marketed as a performance booster as it will just make apps run faster. There could be many apps where users wish they would be a bit faster, and where you have forms with tabs, those forms will load faster for the main tab. Often the tabs which are not the first tab contain secondary information which is not used very often.
There are also some cases where a record is edited triggering an Action or an Automation. This would be a technique to introduce a delay Long enough for the action or automation to process. So then when the user goes to the tab, the data will be there. There are situations now where the record refreshes too quickly upon saving and say a bunch of child records need to be created, but the form refreshes before the Action /Automation completes.
The PM indicated that they planned to make this more widely available and "properly" released in the next month or two. They would need to build the interface for an Admin for an Application to enable it. (It is enabled "per App" and not "per Domain") They will also need to finalize a name for the feature.
Thx Alex for making us aware of this.