"The retailers sold their initial shipment 8 months after the release" is exactly the definition of a flop. Initial shipment is supposed to be the initial sales, not the first year sales. You can say that the numbers are not that bad, but the fact that they sold in 8 months (after price cut) what they expected to sell in the first weeks shows enough.
Only Nintendo said that Labo's success isn't defined by first week sales. Ever since they announced it, they continued to stress that Labo is a long term product with a different sales trajectory. I imagine they made this clear to retailers as well. Not only is it still at the same price, but retailers recently ordered more shipments for 2019. So it's selling well enough to keep going.
Labo is a very different type of product from your typical Switch game, which are expected to do most of their sales in the first few weeks. Nintendo said this numerous times, and still hasn't said otherwise.
They put a lot of efforts and marketing into this thing, took 8 months and the holidays to sell the April launch shipment, and you think that "it sold as expected" and "It's pretty good"?
These aren't my opinions. It came straight from the horse's mouth.
"Nintendo Labo has been positively received as a “Nintendo-like” product since its announcement nearly one year ago. Sales of the three Nintendo Labo kits totaled over 1 million units worldwide as of the end of 2018. Before the first kits launched last April, we expected sales and consumer reception to be different from traditional video games like Mario or Zelda. Nintendo Labo has been incorporated into classes at 100 elementary schools across the US, and has received awards and acknowledgements from various domestic and international media, in categories of toys and of other general consumer products experiences. So, as we expected, it appears that Nintendo Labo has been accepted by our consumers differently than traditional video games."
Why anybody still insists it's a flop even after we have official confirmation that it isn't is beyond me.