A May 2026 arXiv preprint surveys openness at the control plane—the interface between gate-level circuits and physical electronics—across thirteen commercial quantum vendors. The study, a descriptive catalog rather than an empirical benchmark, grades each stack on six axes including pulse-level access, electronics configuration, and calibration data availability. It finds a clear split: IBM ended production pulse control in February 2025 while several mid-tier superconducting and neutral-atom platforms moved toward greater transparency. This preprint has not undergone peer review. The work highlights consequences for reproducibility and cross-vendor benchmarking yet stops short of quantifying how restricted control access slows algorithm-hardware co-design. Related analyses, including a 2024 IEEE survey on quantum software stacks and a 2025 arXiv study on trapped-ion calibration interfaces, show the same pattern: closed control layers force researchers into vendor-specific abstractions that obscure device-specific noise. The original coverage understates the cumulative effect on neutral-atom platforms, which rely on real-time pulse shaping for Rydberg blockade fidelity. Without minimal open control interfaces, hardware-aware compilation techniques developed on one modality cannot transfer, extending the timeline for useful error-corrected logical qubits.