A stall-out is not a breach of the rules any more than throwing a disc into the ground would be. It’s just a turnover.
It’s a little confusing that some of those things listed under turnovers in section 8 (e.g. handover, deflection) do rather sound like breaches of the rules, containing as they do the qualifier ‘intentionally’. But a stall-out has much more in common with an incomplete pass.
The thrower will not intentionally get stalled out – there’s no advantage* – but even if they did, it’s no different to a deliberate turnover for an incomplete pass in huck-and-D. Allowing yourself to turn over is not a breach of the rules.
*(They might occasionally be glad they were stalled out and the 30-yd-backwards incomplete pass doesn’t stand. But that’s not the same as saying they would wish to get stalled out in advance. They would wish even more that they’d hucked it downfield.)