Even if I "hide" the 5ghz, and "forget" the SSID on my android phone

p.s. lowering the 5G Transmit Power is based on the concept that 2.4G WiFi is stronger over distance and through obstacles than 5G WiFi.  This tactic needs to have the smartphone that is configuring the IoT device so far away from the WiFi access point that the 5G signal is unusable and the smart phone connects at 2.4G because it is the only usable connection.  This means that both the smartphone and the IoT device have to be located far away from the WiFi access point.  Most smartphones prefer 5G connections if they are at all possible, conditions have to be "just right" for this tactic to work.  For example, if the IoT device is fixed in place close to the WiFi access point, even a 25% Transmit Power level may be enough to make the smartphone connect at 5G.