> LTE was a huge battery drain at first because they weren't integrated
No, the modem/SoC integration is not a big factor. Having an internal communication inside a single SoC will always be a bit better than going through an external interface, but it's not a significant impact when compared to the total phone power consumption. As other have said, iPhones have an external modem and are fine. Qualcomm insisted on this because they had it, and they're good at marketing.
LTE was a drain at first for the same reason 3G was a drain at first. Cellular standards are designed to have a long life, and are over dimensioned initially. Then Moore law and other optimizations kicks in and make things more acceptable. This is intentional, otherwise the standard would not make the best use of technology over time. And this is something where we need to keep an eye for 5G: Moore law, strictly speaking (higher density for the least cost process. One can still get better, for a higher price) is over. Hopefully 5G will have properly taken this into account.
But then for 5G a big part of the power will be in the RF front-end, with all those antennas. Here too it'll be interesting to see how it evolves over time.
> As other have said, iPhones have an external modem and are fine. Qualcomm insisted on this because they had it, and they're good at marketing.
Addressing the second sentence - I have no knowledge of what transpired but my assumption would be a combination of Apple didn't want to have their SOC's fab'd by Qualcomm for the sake of an integrated modem, and Qualcomm didn't want TSMC fab'ing their modem IP into Apple's SOC's, so the obvious solution was a discrete modem which was a product they could offer.
The wording makes it extremely unclear. Both Company don't "Fab" those SoC. What you are suggesting is Qualcomm doesn't want to give the IP to Apple for Modem SoC Integration, and Apple doesn't want to give their IP to Qualcomm's SoC designed specially for Apple.
While those point are valid they are not the reason Apple have a separate Modem Chip. The design of iPhone had the Modem literally in a completely isolated system, and act more like a USB modem directly connected to the Internal iPhone for security purposes.
And as other have mentioned the integrated of Modem within the SoC have minimal impact to overall battery life.
your understanding is correct except apple everyone else using qualcomm's soc in premium phones uses integrated baseband inside qc's soc. There is one difference though first launches at the time of "G" tansitions i.e. 3g to 4g,4g to 5g also use discrete modems because technology is generally not mature enough to be integrated into soc.
Apple devices (and a handful of android tablets) use separate baseband chips. Most android SoCs have the baseband on the same silicon as the arm cores.
Am I not understanding something here?