If you have the Survival skill, you can use the proficiency bonus on a check to build a lean-to, for example. Navigator tools won't help. Your navigator tools will help your check (proficiency bonus) to determine what day two stars will line up just so at the Druidic Henge opening the gate the Feywild. Survival skill won't help.
The only problem with this is that you are creating an additional situation where you think the tools should apply, even though it isn't stated within the rules of the item that they do.
Granted, this kind of DM adjudication is an important part of the game and I personally think giving the DM this authority to say that Navigation tools should be able to be used for astronomical purposes is a good thing... but when you have a specific rule called out for Navigator's Tools (in this case to avoid getting lost) you are implying that that is the lone use for them.
I think you're better off saying in the Tool description all the things they can be used for (IE star-related information and discovery) and let the DMs decide when to apply it to various checks (of which WIS (Survival) to avoid becoming lost is one of many of them). That way, there's less of a chance of person reading it (as we all have) of that a Skill and a Tool giving the same bonus to the same situation, thereby rendering one of the two completely meaningless.