I'm not the one with the keys to the Web Services. When it happened to me and one of them grabbed the single connection, I had to get other several other people involved because as soon as you'd shut one Web Service down, another would pick up on the connection. It also meant shutting down some services that used other databases for different processes and they were as poorly setup as many of the jobs on SQL Server where you couldn't easily shut down only those parts that were affected by the restore of the one database. That meant that some functionality that shouldn't have needed to "go down" for a long term, did.

I'm also not absolutely positive that immediately switching back to multi- or restricted user would save you if the timing were as unfortunate as what I experienced but it is a command that relies on nothing else and is very fast to execute. Think of it more as hedging a bet. If nothing else, the commented line in the code is a reminder to anyone that may be stepping through the code to troubleshoot (or whatever) to be keenly aware not to lose their SSMS session after setting the database to the single user mode.