Sometimes it can work out, but a good preamp, usually tubes will make the playing field much more fair for DAC shootouts.
Yes a tube pre will equalise the sound qualities in a shootout, with it's own colourations.
DACs just don't have the low output impedance that a good preamp will have.
In regards to the Total or the Bricasti output stages this is definitely not true. They are every bit as good as any preamps output stage. I'll pick on the Bricasti seeing it's jut a smidgen behind the Total in regards to drive and output impedance.
The Total and Bricasti's discrete solid state output stages will shame "nearly" all tube preamps in output impedance and current drive ability, and many solid state pre's as well, in regards to be able to drive into amps with resistive and or capacitive hard loads
The Bricasti's output stage tested driving into a punishing 600ohm load
https://www.stereophile.com/images/212BM1fig12.jpg
This is tube pre PS Audio BHK Signature that has a very good rep (for a tube) to be able into hard loads, into the same 600ohm load as the Bricasti.
https://www.stereophile.com/images/617ps.PSABHKfig6.jpg
Here is an Ayre solid state with 31ohms output impedance with good cred for driving low load impedance's. With the same 600ohm load
https://www.stereophile.com/images/611AK5fig5.jpg
Cheers George