Hi Albert,
If you are asking why there is an account-sync, please take the time to review the
FAQ and
execution guide for FXCM's MT4. I mentioned these two resources in my first post and the webpages are still there for you to view. See the technical support section of the FAQ in particular. Many of the questions you are asking are answered.
Nonetheless, I will take the time to go over more of it in detail. MT4 was designed for dealing desk execution (whereby your broker is acting as the market maker). MT4 has a front end which is what you download onto your computer and use to place trades. And there is a back-end which the broker can use to operate it's dealing desk and accounting purposes. Metaquotes designed this as a turn-key package for brokers who wanted to easily setup their own forex offering. This is why the vast majority of MT4 firms operate a dealing desk and have not designed their own platform. Many MT4 brokers don't have account syncs or balance adjustments because they operate a dealing desk which uses the MT4 back-end execution and reporting, but again you're trading with a dealing desk.
FXCM does not have a dealing desk or make the market, therefore MT4's back-end is not used. A technology bridge is used to integrate the MT4 interface into FXCM's NDD forex execution back-end and accounting. You can think of the technology bridge as the communication link transmitting ordesr between MT4 and FXCM. Even though there is this communication between the two, there are still limitations in the design of MT4 which can hinder communication. That is why you will see an account sync to bring your MT4 balance in line with the FXCM balance due to rollover, withdrawals, deposits, etc. If the MT4 platform you are using does not use a balance adjustment or require you to monitor their own accounting system, then there is a high likelihood the broker is using dealing desk execution. In fact, there are multiple brokers which require the same time of monitoring of a read-only statement to confirm execution such as FXCM requires.
I'm happy that you know how to check the read-only statement to confirm trading activity, and this is what all traders should be doing on the MT4 platform if they have any questions about an account sync or need to verify the execution of a trade.
-Jason