[Bugfix][BAGEL] Restore original denoise step count (#7049)

Signed-off-by: Trigger <Meng.Bo.Wang@outlook.com>
Signed-off-by: Gao Han <hgaoaf@connect.ust.hk>
Co-authored-by: Gao Han <hgaoaf@connect.ust.hk>

docs/user_guide/diffusion/execution_modes.md

@@ -99,10 +99,10 @@ step-wise continuous batching for image generation with `bagel.yaml`,
 `bagel_think.yaml`, and `bagel_single_stage.yaml`. In the two-stage topologies,
 only the diffusion stage uses step execution; the autoregressive Thinker is
 unchanged. Explicit text-output requests in the single-stage topology retain
-the complete-request path. BAGEL schedules exactly `num_inference_steps`
-denoising updates, so one-step image requests are supported. BAGEL step
-execution does not currently support sequence parallelism or a diffusion cache
-backend. HunyuanImage3 also supports step execution, but only
+the complete-request path. Use at least two inference steps for BAGEL image
+requests because BAGEL schedules `num_inference_steps - 1` denoising updates.
+BAGEL step execution does not currently support sequence parallelism or a
+diffusion cache backend. HunyuanImage3 also supports step execution, but only
 when its resolved self-attention backend is `TORCH_SDPA`;
 set `DIFFUSION_ATTENTION_BACKEND=TORCH_SDPA` or configure
 `diffusion_attention_config.default.backend=TORCH_SDPA` before using