Thats not as much of a concern as the Chinese government taking control, pushing malicious updates, and or siphoning information from these devices through legit C&C servers in china. OEM malware would be easy to see, and not reliably allow timing of deployment of malware to make the attack more effective.
What do you mean when you say "these" devices? I have never seen any credible report claiming a Huawei was pwned by any government.
Its like the kaspersky issue. Its not that kaspersky is innately a problem, but the potential Russian control over that company does not give a lot of confidence.
When Kaspersky was banned, there were credible reports that they had been used by Russia to attack US intelligence services.
Also, the ban on Kaspersky is limited to US government employees. Everybody else can still use their products (if they trust them... I wouldn't). The Huawei ban applies to everyone all over the world.
But mostly it's the lack of justification that concerns me, not the scope of the ban. The Kaspersky ban had plenty of justification.