They don't necessarily overlap; all spouses are (optimistically) life partners, but not all life partners are spouses. That might be by choice (because the partners don't believe in marriage, for example) or necessity (if they cannot legally marry for some reason).
I can imagine many questions that will be different depending on whether the relationship is formalized in a traditional way. For example:
"How can I get my family and friends to treat my life partner like my husband/wife, even though we can't legally marry where we live?"
"My life-partner and I are splitting; how can we do this amicably when there is no legal framework like divorce?"
"My spouse and I lived together for five years before we got married last year. Ever since the wedding, it seems like our relationship has completely changed. What's going on?"
And so forth.
If it turns out that the vast majority of questions don't have anything to do with the specific legal status of the relationship then it could make sense to lump all these together, but it seems rather early to make that call.