DLC was not originally planned to be a thing at all. Believe if you want, here is what happened:

>E3 2019 was an absolute disaster for the morale of the company. Masuda may not like to admit it, but they fucked up and he knows.
>GameFreak only told us the dex cut was coming at all to prevent even bigger backlash around release. The cut was not originally planned, it was a relatively recent decision due to general development problems.
>SWSH were rushed games, Nintendo demanded a Winter 2019 release so SWSH Special Edition Switch Consoles could be sold.
>SWSH was already behind schedule in various ways, day one patch fixed a lot of issues.
>GameFreak was not able to prepare for another 2020 release this quickly, the DLC was an Emergency Measure to push out new design for the Merchandising aspect of the Pokemon IP
>DLC was relatively low effort and development was already done mid 2020 on both packs. Notice how when the DLC was announced, all they had was concept art?

That is all. Next Pokemon game 2021, but Centro already revealed that "surprise" (it's not too surprising lol)