If the SE is using Apple's modem then pretty good chance it won't have mmWave. Getting the modem 'done' has been an issue and if they can skip a whole frequency band that (and associated features) that would make the product easier to finish. Generation 1.0 modem just won't go into high end iPhones. most iPads and the SE would give them substantial v1.0 volume to work with.
Even if it is Qualcomms there are modules and licensing they can skip buying ( which in part is why not there on SE3. )
The SE4 is on a bill of materials budget. For example.
".. Apple has reportedly been holding out for $25 per panel, but Samsung's final offer was $30, which is lower than the two Chinese manufacturers. That leaves BOE and Tianma as potential suppliers, however Tianma has not yet met Apple's stringent quality requirements, leaving BOE in pole position to win the majority of the orders, if not all of them. ... "
Apple supplier BOE has taken the lead in becoming the OLED panel supplier for the fourth-generation iPhone SE, IT Home reports. Samsung Display,...
www.macrumors.com