Older versions of the kernel did. It was dropped I think for the kernels that came with new batch ones though.
You are not going to easily get the newer revisions of the cart to work with the older kernels, if you wanted to downgrade (which would cost you autopatching and SDHC support) your older model EZ4 then you could.
The way it worked was to have two separate loaders in there, and a small thing to tell it which it was running on/as to choose which one to go into.
Frankly the only really good reason to run DS mode on an EZ4 any more is to run DS ROM/save dumping tools, and if you have a CFW 3ds then that is even easier. Commercial game wise it will likely not support much past about April 2009 (about ROM number 3600 in whatever numbering system you are using).