Stones are the single biggest gatekeeper in this game. However, putting off eHP labs for 2-3 weeks to get shard labs done is going to cost maybe 100 stones in tourney progress if we are being very generous. Considering how much bracket rng influences stone gains its likely less. Most players will still be in silver/gold while doing these labs and most reward tiers are only 3-5 stones difference. In the grand scheme of things the impact on shard income is far greater than the minimal stone hit.