Nintendo has already published 5 retail games this year, including two new releases in major long-running series, one of which has sold over 20 million units. This in pretty similar to previous years in the Switch's llifespan, especially when you consider that Nintendo usually hold their most significant titles for September - December. So there's no sign in the months that have already come and gone that Nintendo is stockpiling finished games for a hypothetical Switch Pro (which may not be "pro" at all, but something else entirely).
The only real evidence in support of the game-hoarding theory is the lack of titles announced for the fall, but there are multiple alternate explanations for that:
1. There are major games coming for the holiday season, but they haven't been announced yet because the pandemic scrambled Nintendo's PR strategy. (We have enough reporting to know the latter is definitely true.)
2. The games that would have launched this holiday have been delayed because of the impact of COVID on development.
3. Games that were targeting Holiday 2020 ran into development issues before the pandemic hit (this could be the case with Bayonetta 2 and BotW 2) and, as a result, Nintendo was always going to have a year that leaned heavily on remasters and "definitive" ports of older games. (Seems like Emily might have hinted at this earlier this year.)
4. Some combination of the above. (This is most likely, of course.)
Of course, Nintendo may also have moved around the release dates of a game or two to better coincide with the launch of the revision, but thinking that they'd tank their 2020 lineup just to have a big revision launch seems like a stretch, given what we know now.