Today is 21 days since the e-file date, and the return is still not here. Is the full bar arbitrary or is it actually indicating that something was done on their end?

Unfortunately TurboTax gets no information about the status of your refund.
In normal times, the IRS says that most filers get their refunds within 21 days from the time their tax return is accepted. Since TurboTax gets no information about status, the bar in TurboTax will not tell you anything. 
Many returns are taking longer now since the IRS did not process returns for a while and there is now a big backlog of unprocessed returns.
Some press reports stated the IRS has started reopening offices and processing centers and are starting to process mailed returns again after not processing any for several weeks but no IRS press release has confirmed this.
They are now taking phone calls with a limited staff but it's hard to get through.

If you efiled your return, have you confirmed that the return was submitted by TurboTax and accepted by the IRS?
https://shop.turbotax.intuit.com/efile/efile_status_lookup.jsp

If accepted, what does the IRS tracking web site say about the status of your refund?
https://www.irs.gov/refunds

Here is an IRS Q&A with information about refunds:
https://www.irs.gov/refunds/tax-season-refund-frequently-asked-questions

The refund indicator on the TurboTax Tax Home web page is only an estimate based on the IRS target of 21 days from accepting a tax return to issuing a tax refund.  This target was established for a normal tax season.  This is Not a Normal tax season, what with the pandemic and then with the stimulus, it has left the IRS severely under-manned.

Use the IRS website for the status of a federal tax refund since it has the most reliable and accurate information - https://www.irs.gov/refunds