This rumor makes no sense at face value. The in-game charts are all designed to be variable width inputs placed at any point along the track (that's not quite true, but a close enough approximation) and can support several inputs at once (and does happen on the Master and Append difficulties). They would need to redo all of the charts to make that work with either a keyboard or controller, which isn't impossible (it's what Touhou Danmaku Kagura did with its PC version) but would they even want to put in that kind of work? That and I think the PC/console playerbase would be much less friendly to your typical F2P structure for a game like this, it seems like pretty different groups of playerbases. I'm just not sure what the market here for this is, especially since they would already be getting most of the possible casual playerbase from the mobile version.
I guess playing on a keyboard as-is may be technically possible, in the same way you could theoretically play Chunithm on a keyboard with enough inputs, but that seems like it would be a miserable experience.
Maybe if this was a spin-off with a more traditional N-lane layout (or something a little weirder, like how Ongeki works) that would be viable to be played on a controller or keyboard... but that's not what this rumor is.