Does it work at the moment?
Yes it is and since the mempool is no longer congested, a lot of people no longer have to use it which is why you can still enter your transaction hash even if it's not exactly XX:00:00 (I just entered one at XX:04 and it was accepted).
Fee's are also way cheaper now compared on december or so when the mempool is still congested.
sorry, I also do not quite understand this,
but if we are not sure better not use this service
Seems like you're not familiar with viabtc... It's a mining pool and they have this service that will let you include your transaction in the next block they mine.
A lot of people have already used this but the problem is when there is too much people using it causing the service not to work or decrease your chance getting your transaction inlcuded in their queue which actually happened in the last few months.