It's definitely not a given that a new device will support E5a/L5. This article explains the details better - https://barbeau.medium.com/crowdsourcing-gnss-capabilities-of-android-devices-d4228645cf25. It's often a cost function of the device, as even if a device ships a chipset that supports dual-frequency it may not be enabled. For example, the Galaxy S21 (Snapdragon and Exynos variants) do not support dual-frequency, while the S21+ and Ultra (Snapdragon and Exynos variants) do, despite the S21, S21+, and S21 Ultra sharing the same chipsets.