I personally would consider Quicken Loans to be a reputable mortgage lender. They may not be the cheapest, but in my experience they are competitive and their customer support is very good. The most likely reason for them not being able to provide a rate is that it is somewhat dependent on the property you choose.
Your statement is a little confusing here:
They said that I would have to first lock in on a home before those details would be provided.
The word "lock" is typically used to "lock in a rate" but you don't "lock in a home". I think all they're saying is they need to enter in an address into their system before it will spit out a rate. You can probably enter in any address for one of the homes you're considering to get a ballpark rate.
Once you get a rate and you are strongly considering purchasing a particular home, then you can "lock your rate" for that home. All "locking the rate" means is that if mortgage rates change in the next X days (typically 30-40 days), you are guaranteed the rate you locked (whether rates go up or down). Note this doesn't marry you to that particular lender. If you shop around after locking a rate you can still use a different lender, though if you do that I'd highly recommend asking your lender if they can match the competing offer first, since maybe they can and you already have a relationship with them.
As a side note, I once received a quote from Quicken Loans that was decent, and I think I even locked in the rate. I then got another quote from a friend of mine who is a mortgage broker which was significantly better. (He was doing me favor and foregoing his commission.) I then presented his offer to my Quicken Loans rep and they were nice enough to tell me that it was a fantastic deal and that I should take it. Even though I didn't end up financing with Quicken Loans, I found my experience with them to be very good, as well as efficient.