Hi!
Welcome to the forum.
The English translations sometimes do not make sense as the real message got lost in translation.
Maybe the L88 manual was written before the introduction of the S88DC modules.

You do not need relays when using the S88DC modules.
You can use relays directly with the L88 instead of using S88DC modules.

When using relays with three-rail, the relay can share a common ground with the outer rail. For two-rail there cannot be a common ground between the relay and one of the rails. And the other options shown - like contact track and circuit track - are not available for two-rail.

Hi Vedat

First I am not a 2 rail specialist although long time ago (1975 to 1982) I had an N scale layout with current detection (French manufacturer Lybe). So here is my understanding on the Märklin S88 for 2 rails DIGITAL.

The manual is available here (english sections from page 8 until 11 )https://static.maerklin....1d49346e751579266054.pdf

The S88 DC (60882) has 16 current-sensing entries (5 mA or more) grouped on 2 blocs sharing the same common.
There is a confusion here because in normal 2 rails you have to swap the poles to change the loco's direction. This is not the case in digital 2 rails.
In case you use separate feed circuits (booster) then the current sensor return MUST be connected to the appropriate booster.
Already in HO you may have a middle size layout with only one feeding source (I have 32 locos sound digital HO fed by one CS3 and one 60101)

Sorry for the long explanation but you can use the current-sensing feature in 2 rails and in combination with resistive axles all vehicles are detected OK.
In those days of my N scale layout, the axles were made resistive by using a graphite spray used on CRTs to have a resistor for each axle of approx 10 kOhms
Now, some are selling N scale axles with a SMD resistor on it. Graphite sprays are still available. Spray some paint in a bottle cap and use a small brush to apply the paint over the axle insulation ring AND LET IT FULLY DRY before use. Check the resistor value. Finished
So that the little I know on the subject. I hope this helps.
Cheers
Jean

Hi Vedat

"In the above drawing, since the block section is isolated from the rest of the track, the decoder detects presence of a loco on that section, but to keep the loco moving, does it also feed current to the blocked track section?"
Yes it does feed the rest of the isolated track section. Also notice, if you use stop sections, you must use use a 1.5 kOhm resistor between the current sensing zone and the stop zone.
If you use a train control software like Rocrail, you don't need those stop sections and the resistors, thus simplifying the wiring.

Only restrictions are:
- there is a small voltage drop (0.6 to 1.2 V) because of the current sensing circuit (you may notice a very small slow-down on some locos)
- the maximum current is limited by the diode current capacity (better avoid derailing in current-sensing areas)

Cheers
Jean

Hi Vedat
Not 100% sure but usually train control software like Train Controller feed on collection data on sensors and command locos by digital orders thus making stop sections useless. This is for sure the case with Rocrail which is an excellent software for all systems in (30+ various digital units) 20+ languages and a free donation mode (you first use it FOR FREE and then you donate what you want, when you want. The very best software in my opinion
Here it is in operation on my layout with a CS3

Cheers
Jean