The definition of what constitutes a "revenue bill" is still up for grabs, since the founders left the definition so vague. Over time, the courts and House custom have determined the Senate can perform this switcheroo as long as the Senate does not initiate bills whose primary purpose is raising funds for the general operation of the federal government. The House, often finding the parliamentary procedure in its interest, has objected only a little more than once a year over the last 20 years. Both Republicans and Democrats have used the trick while in the majority. Even in this season of hair-trigger umbrage, Republican Senate leadership aides aren't very worked up that Democrats are going to invoke this standard procedure.
You can, however, make the case that the dual-track approach is a part of the general hurry-up strategy that is a blow to transparency and thorough consideration. Administration and Democratic leaders have always believed that any delay in the process gives critics more time to gather strength. If the Senate were not allowed to begin debate until it received the House bill, that would extend the process a few weeks.
Some conservatives worry the shell bill might turn into a shell game. Because the shell bill started in the House, it is possible House Democratic leaders could vote on it directly after the Senate is done with its work. That would really speed up the process. There would be no House amendments, no debate about those amendments, and no conference process to reconcile House and Senate versions of the health care legislation.
When House Majority Leader Steny Hoyer was asked whether he might take this expedited approach, he ducked, refusing to rule it out, which undoubtedly made many Republicans nervous. But leadership aides in both chambers say this scenario is far-fetched. It would require House Democrats to shelve all of their ideas about health care and remove themselves from the process, which isn't going to happen. That's probably good—because then health care reform would win a name unmentionable in polite company.