I hope but shouldn't a technical preview have the core almost finished, cause if you are waiting until the end to fix something that is part of the core of the OS, it's not good planning.
As far as loading/resuming is concerned, I'd be very much surprised if MS were able to remove it entirely. I don't know why this issue, which has been with us since WP7, has persisted for so long, but it seems to be systemic.
Still, the answer to your question is "No". While it's true that some things must be closer to finished than others, these are typically things we as end users never see, and usually have no idea they even exist.
I also dispute that we can know how well MS is planning their work on W10M. For example, the overly lengthy loading/resuming delays (even for WP) some are reporting, could potentially be an issue with firmware. Firmware is always implemented last, and is not part of the core OS, meaning this delay may not be a bug at all, but rather just the consequence of device specific software components not yet existing. We just don't and can't know...
If software were a house, a painter having missed a spot in the kitchen could affect the house in a way as to make it look as if a bomb went off in the basement. This is so completely different from what most people consider intuitive that it makes most judgements of unfinished software by laymen pretty much meaningless. Judging the progress of software development requires you to forget most of what you know about how material products evolve. It's easy to grasp how far along the building of a bridge, sculpture or house has progressed, but that intuitive approach simply doesn't apply to software. None of us can really judge W10M's progress without access to a lot more information than any of us currently have.
An example would be the last preview build. MS stated that they fixed over 2000 issues and bugs. How many in this forum could name even 1% of those addressed issues? That demonstrates that MS's progress or speed is not really the problem people think it is. The real issue is people's inability to see even 1% of the progress being made. That is obviously bound to influence people's perceptions in a negative way.
All of this represents a very large risk in terms of how people perceive MS and the W10M preview. We can see this now in the forums in how some people are starting to doubt MS' software competence, or in threads such as this one. I suppose MS thinks the benefits outweigh the risks.
Anyway, last but not least, it seems a lot of people are expecting to get their final/official W10M update in October. People simply can't imagine how the preview could improve "enough" by then. I doubt anybody with an existing device will have W10M officially by October however. October is when MS will release W10M to OEMs. OEMs, including MS, may still have to build drivers and firmware for their own devices, meaning there may be more time than many of us think.