We need the devices to meet our requirements so that's the main limitation. The current generation Snapdragon 8 Elite Gen 5 is the only one providing hardware memory tagging (MTE). Even the slightly lower end Snapdragon 8 Gen 5 doesn't support MTE. The next generation flagship SoC has improvements needed to meet our requirements. There's still going to be a lot of porting and integration work. We'll be the first ones using MTE for the whole kernel and OS as we are on Pixels so there's going to be a lot to deal with for it. For Pixels, Google did do testing for MTE across the OS internally but even on Pixels it isn't perfectly supported and we have to fix a lot of memory corruption bugs it finds in both the kernel and userspace.

I would bet that what Motorola can change without trouble on the lower end is more restricted, too. Generally low end models use more parts that are old, off the shelf, and/or shared with several other models to keep costs low, and so major changes can quickly balloon costs.