David,
Good questions. Truth be told,
no method of carpet cleaning can truly "sanitize" a carpet. Some methods pull more contaminants from the carpet than others. And HWE has the potential to recover the highest amount of soil in a single shot. Encap is intended to serve as a maintenance system that will keep the carpet looking better/longer between HWE cleanings. However no method of carpet cleaning can honestly be touted as "sanitizing" a carpet.
To answer your question about after sprays. Avoid them. Applying additional chemistry to the encap process will invariably mess up the crystallization process.
Some time ago we heard from a cleaner who told us the schools he was cleaning with Releasit were testing better than other schools in his state. Their school district tested the school's carpets for mold content and the cleaner told us that his schools were testing with lower mold content than other schools in his state. Well that got us to thinking; perhaps the polymer was holding the mold in suspension. So we had a lab scientist do some testing with Releasit. Here is a PDF of the test results...
http://www.excellent-supply.com/Polymers_role_in_reduction_of_mold_in_carpets.pdf
Please do NOT take this test as a statement that Releasit is an anti-mold product. We are not stating that at all. All we're noting from this test is that there was an interesting quantifiable reduction in mold in a carpet that was cleaned with Releasit. A lot more testing would need to be done in order to confirm what we saw in this singular test. Yet, these test results were interesting to see.
My reason for referring to the test here is that this research seems to indicate that the polymer may be capable of holding certain types of contaminants in a polymerized state, thereby possibly reducing the contaminants impact on the indoor environment. But as I said above, NO method of cleaning should be considered to be a sanitizing method of carpet care (not encap, not even HWE). And I do agree with your conclusion, HWE would be a better choice when cleaning in health sensitive areas such as daycare centers, etc.
The encapsulation method is intended for keeping typical commercial carpets looking their best between periodic HWE cleanings. It affords the building occupants the opportunity to enjoy cleaner looking carpets on a day-in day-out basis. And it enables the carpet cleaner to provide the service in a profitable manner. Thus in its intended application, encap becomes a win win for both parties.
Rick Gelinas