@ Work, as you stated, application. In the case of a tower, no gel, but in the case of UG, gel. Usually it gets transitioned somewhere if it goes from UG to riser. I'm pretty sure it's the 50' rule also for buildings, but would need to look it up. Usually it's a combination of the gel being possibly flammable and the cabling not being rated the same as indoor or GP cable.
@ Mike, think of it this way, Elk may be aware of how the product gets installed and/or their components, but in the specifics, they can't put the manual or documents together to be a "how to" for anyone installing a system. It's like purchasing a desktop computer; the basics of how to connect all the components together are there (even color coded on some) but if you want to get it on your network, DNS it and the like, there are some other steps involved not covered in the basic windows configuration. They may state you need to connect to your ISP, but say you have multiple computers and a single modem? Does your ISP or computer vendor tell you that you must install and configure a router behind the modem or install a dumb switch?
Some manuals and docs spell out certain items, such as cable ratings that must be used, types, etc. and others use boilerplate terms (meet applicable code, etc.) but a install manual can never be used or classified as a system design guide. Elk did, however, change in the years and started supplying a surge with every M1 panel that goes out the door for telephone connection, but not one for AC power.....think about that.